diff --git a/composer.json b/composer.json
index ad67dc3e9..b772f9546 100644
--- a/composer.json
+++ b/composer.json
@@ -79,7 +79,7 @@
     ],
     "scripts": {
         "compile": "@php -dphar.readonly=0 bin/compile",
-        "test": "simple-phpunit",
+        "test": "@php simple-phpunit",
         "phpstan-setup": [
             "@composer config platform --unset",
             "@composer update",
diff --git a/doc/03-cli.md b/doc/03-cli.md
index 12125919c..727e5fc5d 100644
--- a/doc/03-cli.md
+++ b/doc/03-cli.md
@@ -117,7 +117,10 @@ resolution.
   See also the [`platform`](06-config.md#platform) config option.
 * **--ignore-platform-req:** ignore a specific platform requirement(`php`,
   `hhvm`, `lib-*` and `ext-*`) and force the installation even if the local machine
-  does not fulfill it. Multiple requirements can be ignored via wildcard.
+  does not fulfill it. Multiple requirements can be ignored via wildcard. Appending
+  a `+` makes it only ignore the upper-bound of the requirements. For example, if a package
+  requires `php: ^7`, then the option `--ignore-platform-req=php+` would allow installing on PHP8,
+  but installation on PHP 5.6 would still fail.
 
 ## update / u
 
@@ -202,7 +205,10 @@ php composer.phar update vendor/package:2.0.1 vendor/package2:3.0.*
   See also the [`platform`](06-config.md#platform) config option.
 * **--ignore-platform-req:** ignore a specific platform requirement(`php`,
   `hhvm`, `lib-*` and `ext-*`) and force the installation even if the local machine
-  does not fulfill it. Multiple requirements can be ignored via wildcard.
+  does not fulfill it. Multiple requirements can be ignored via wildcard. Appending
+  a `+` makes it only ignore the upper-bound of the requirements. For example, if a package
+  requires `php: ^7`, then the option `--ignore-platform-req=php+` would allow installing on PHP8,
+  but installation on PHP 5.6 would still fail.
 * **--prefer-stable:** Prefer stable versions of dependencies.
 * **--prefer-lowest:** Prefer lowest versions of dependencies. Useful for testing minimal
   versions of requirements, generally used with `--prefer-stable`.
diff --git a/src/Composer/DependencyResolver/Problem.php b/src/Composer/DependencyResolver/Problem.php
index deb39d5f6..836f308b4 100644
--- a/src/Composer/DependencyResolver/Problem.php
+++ b/src/Composer/DependencyResolver/Problem.php
@@ -15,6 +15,7 @@ namespace Composer\DependencyResolver;
 use Composer\Package\CompletePackageInterface;
 use Composer\Package\AliasPackage;
 use Composer\Package\BasePackage;
+use Composer\Package\Link;
 use Composer\Package\PackageInterface;
 use Composer\Package\RootPackageInterface;
 use Composer\Pcre\Preg;
@@ -242,19 +243,19 @@ class Problem
                 $ext = substr($packageName, 4);
                 $msg = "- Root composer.json requires PHP extension ".$packageName.self::constraintToText($constraint).' but ';
 
-                if (extension_loaded($ext)) {
-                    $version = self::getPlatformPackageVersion($pool, $packageName, phpversion($ext) ?: '0');
-
-                    if (null === $version) {
-                        return array($msg, 'the '.$packageName.' package is disabled by your platform config. Enable it again with "composer config platform.'.$packageName.' --unset".');
+                $version = self::getPlatformPackageVersion($pool, $packageName, phpversion($ext) ?: '0');
+                if (null === $version) {
+                    if (extension_loaded($ext)) {
+                        return array(
+                            $msg,
+                            'the '.$packageName.' package is disabled by your platform config. Enable it again with "composer config platform.'.$packageName.' --unset".',
+                        );
                     }
 
-                    $error = 'it has the wrong version ('.$version.') installed';
-                } else {
-                    $error = 'it is missing from your system';
+                    return array($msg, 'it is missing from your system. Install or enable PHP\'s '.$ext.' extension.');
                 }
 
-                return array($msg, $error.'. Install or enable PHP\'s '.$ext.' extension.');
+                return array($msg, 'it has the wrong version installed ('.$version.').');
             }
 
             // handle linked libs
@@ -431,11 +432,31 @@ class Problem
         $available = $pool->whatProvides($packageName);
 
         if (count($available)) {
-            $firstAvailable = reset($available);
-            $version = $firstAvailable->getPrettyVersion();
-            $extra = $firstAvailable->getExtra();
-            if ($firstAvailable instanceof CompletePackageInterface && isset($extra['config.platform']) && $extra['config.platform'] === true) {
-                $version .= '; ' . str_replace('Package ', '', $firstAvailable->getDescription());
+            $selected = null;
+            foreach ($available as $pkg) {
+                if ($pkg->getRepository() instanceof PlatformRepository) {
+                    $selected = $pkg;
+                    break;
+                }
+            }
+            if ($selected === null) {
+                $selected = reset($available);
+            }
+
+            // must be a package providing/replacing and not a real platform package
+            if ($selected->getName() !== $packageName) {
+                /** @var Link $link */
+                foreach (array_merge(array_values($selected->getProvides()), array_values($selected->getReplaces())) as $link) {
+                    if ($link->getTarget() === $packageName) {
+                        return $link->getPrettyConstraint().' '.substr($link->getDescription(), 0, -1).'d by '.$selected->getPrettyString();
+                    }
+                }
+            }
+
+            $version = $selected->getPrettyVersion();
+            $extra = $selected->getExtra();
+            if ($selected instanceof CompletePackageInterface && isset($extra['config.platform']) && $extra['config.platform'] === true) {
+                $version .= '; ' . str_replace('Package ', '', $selected->getDescription());
             }
         } else {
             return null;
diff --git a/src/Composer/DependencyResolver/RuleSetGenerator.php b/src/Composer/DependencyResolver/RuleSetGenerator.php
index 94c834841..9164c333a 100644
--- a/src/Composer/DependencyResolver/RuleSetGenerator.php
+++ b/src/Composer/DependencyResolver/RuleSetGenerator.php
@@ -12,6 +12,7 @@
 
 namespace Composer\DependencyResolver;
 
+use Composer\Filter\PlatformRequirementFilter\IgnoreListPlatformRequirementFilter;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterFactory;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterInterface;
 use Composer\Package\BasePackage;
@@ -197,11 +198,14 @@ class RuleSetGenerator
             }
 
             foreach ($package->getRequires() as $link) {
+                $constraint = $link->getConstraint();
                 if ($platformRequirementFilter->isIgnored($link->getTarget())) {
                     continue;
+                } elseif ($platformRequirementFilter instanceof IgnoreListPlatformRequirementFilter) {
+                    $constraint = $platformRequirementFilter->filterConstraint($link->getTarget(), $constraint);
                 }
 
-                $possibleRequires = $this->pool->whatProvides($link->getTarget(), $link->getConstraint());
+                $possibleRequires = $this->pool->whatProvides($link->getTarget(), $constraint);
 
                 $this->addRule(RuleSet::TYPE_PACKAGE, $this->createRequireRule($package, $possibleRequires, Rule::RULE_PACKAGE_REQUIRES, $link));
 
@@ -225,11 +229,14 @@ class RuleSetGenerator
                     continue;
                 }
 
+                $constraint = $link->getConstraint();
                 if ($platformRequirementFilter->isIgnored($link->getTarget())) {
                     continue;
+                } elseif ($platformRequirementFilter instanceof IgnoreListPlatformRequirementFilter) {
+                    $constraint = $platformRequirementFilter->filterConstraint($link->getTarget(), $constraint);
                 }
 
-                $conflicts = $this->pool->whatProvides($link->getTarget(), $link->getConstraint());
+                $conflicts = $this->pool->whatProvides($link->getTarget(), $constraint);
 
                 foreach ($conflicts as $conflict) {
                     // define the conflict rule for regular packages, for alias packages it's only needed if the name
@@ -277,6 +284,8 @@ class RuleSetGenerator
         foreach ($request->getRequires() as $packageName => $constraint) {
             if ($platformRequirementFilter->isIgnored($packageName)) {
                 continue;
+            } elseif ($platformRequirementFilter instanceof IgnoreListPlatformRequirementFilter) {
+                $constraint = $platformRequirementFilter->filterConstraint($packageName, $constraint);
             }
 
             $packages = $this->pool->whatProvides($packageName, $constraint);
diff --git a/src/Composer/DependencyResolver/Solver.php b/src/Composer/DependencyResolver/Solver.php
index 9b112d87f..28b9e40da 100644
--- a/src/Composer/DependencyResolver/Solver.php
+++ b/src/Composer/DependencyResolver/Solver.php
@@ -12,6 +12,7 @@
 
 namespace Composer\DependencyResolver;
 
+use Composer\Filter\PlatformRequirementFilter\IgnoreListPlatformRequirementFilter;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterFactory;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterInterface;
 use Composer\IO\IOInterface;
@@ -174,6 +175,8 @@ class Solver
         foreach ($request->getRequires() as $packageName => $constraint) {
             if ($platformRequirementFilter->isIgnored($packageName)) {
                 continue;
+            } elseif ($platformRequirementFilter instanceof IgnoreListPlatformRequirementFilter) {
+                $constraint = $platformRequirementFilter->filterConstraint($packageName, $constraint);
             }
 
             if (!$this->pool->whatProvides($packageName, $constraint)) {
diff --git a/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php b/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
index de1388edd..4e3ac7f58 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
@@ -5,20 +5,40 @@ namespace Composer\Filter\PlatformRequirementFilter;
 use Composer\Package\BasePackage;
 use Composer\Pcre\Preg;
 use Composer\Repository\PlatformRepository;
+use Composer\Semver\Constraint\Constraint;
+use Composer\Semver\Constraint\ConstraintInterface;
+use Composer\Semver\Constraint\MatchAllConstraint;
+use Composer\Semver\Constraint\MultiConstraint;
+use Composer\Semver\Interval;
+use Composer\Semver\Intervals;
 
 final class IgnoreListPlatformRequirementFilter implements PlatformRequirementFilterInterface
 {
     /**
      * @var string
      */
-    private $regexp;
+    private $ignoreRegex;
+
+    /**
+     * @var string
+     */
+    private $ignoreUpperBoundRegex;
 
     /**
      * @param string[] $reqList
      */
     public function __construct(array $reqList)
     {
-        $this->regexp = BasePackage::packageNamesToRegexp($reqList);
+        $ignoreAll = $ignoreUpperBound = array();
+        foreach ($reqList as $req) {
+            if (substr($req, -1) === '+') {
+                $ignoreUpperBound[] = substr($req, 0, -1);
+            } else {
+                $ignoreAll[] = $req;
+            }
+        }
+        $this->ignoreRegex = BasePackage::packageNamesToRegexp($ignoreAll);
+        $this->ignoreUpperBoundRegex = BasePackage::packageNamesToRegexp($ignoreUpperBound);
     }
 
     /**
@@ -31,6 +51,33 @@ final class IgnoreListPlatformRequirementFilter implements PlatformRequirementFi
             return false;
         }
 
-        return Preg::isMatch($this->regexp, $req);
+        return Preg::isMatch($this->ignoreRegex, $req);
+    }
+
+    /**
+     * @param string $req
+     * @return ConstraintInterface
+     */
+    public function filterConstraint($req, ConstraintInterface $constraint)
+    {
+        if (!PlatformRepository::isPlatformPackage($req)) {
+            return $constraint;
+        }
+
+        if (!Preg::isMatch($this->ignoreUpperBoundRegex, $req)) {
+            return $constraint;
+        }
+
+        if (Preg::isMatch($this->ignoreRegex, $req)) {
+            return new MatchAllConstraint;
+        }
+
+        $intervals = Intervals::get($constraint);
+        $last = end($intervals['numeric']);
+        if ($last !== false && (string) $last->getEnd() !== (string) Interval::untilPositiveInfinity()) {
+            $constraint = new MultiConstraint(array($constraint, new Constraint('>=', $last->getEnd()->getVersion())), false);
+        }
+
+        return $constraint;
     }
 }
diff --git a/src/Composer/Installer.php b/src/Composer/Installer.php
index ebdc30caa..c78dc8fd7 100644
--- a/src/Composer/Installer.php
+++ b/src/Composer/Installer.php
@@ -28,6 +28,7 @@ use Composer\DependencyResolver\SolverProblemsException;
 use Composer\DependencyResolver\PolicyInterface;
 use Composer\Downloader\DownloadManager;
 use Composer\EventDispatcher\EventDispatcher;
+use Composer\Filter\PlatformRequirementFilter\IgnoreListPlatformRequirementFilter;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterFactory;
 use Composer\Filter\PlatformRequirementFilter\PlatformRequirementFilterInterface;
 use Composer\Installer\InstallationManager;
@@ -807,15 +808,16 @@ class Installer
 
         $rootRequires = array();
         foreach ($requires as $req => $constraint) {
+            if ($constraint instanceof Link) {
+                $constraint = $constraint->getConstraint();
+            }
             // skip platform requirements from the root package to avoid filtering out existing platform packages
             if ($this->platformRequirementFilter->isIgnored($req)) {
                 continue;
+            } elseif ($this->platformRequirementFilter instanceof IgnoreListPlatformRequirementFilter) {
+                $constraint = $this->platformRequirementFilter->filterConstraint($req, $constraint);
             }
-            if ($constraint instanceof Link) {
-                $rootRequires[$req] = $constraint->getConstraint();
-            } else {
-                $rootRequires[$req] = $constraint;
-            }
+            $rootRequires[$req] = $constraint;
         }
 
         $this->fixedRootPackage = clone $this->package;
diff --git a/tests/Composer/Test/Fixtures/installer/platform-ext-solver-problems.test b/tests/Composer/Test/Fixtures/installer/platform-ext-solver-problems.test
index aea9122b8..be8313f55 100644
--- a/tests/Composer/Test/Fixtures/installer/platform-ext-solver-problems.test
+++ b/tests/Composer/Test/Fixtures/installer/platform-ext-solver-problems.test
@@ -47,7 +47,7 @@ Your requirements could not be resolved to an installable set of packages.
 
   Problem 1
     - Root composer.json requires a/a * -> satisfiable by a/a[1.0.0].
-    - a/a 1.0.0 requires ext-filter 2.0.0 -> it has the wrong version (7.4.0; overridden via config.platform, actual: %s) installed. Install or enable PHP's filter extension.
+    - a/a 1.0.0 requires ext-filter 2.0.0 -> it has the wrong version installed (7.4.0; overridden via config.platform, actual: %s).
 
 To enable extensions, verify that they are enabled in your .ini files:
 __inilist__
diff --git a/tests/Composer/Test/Fixtures/installer/solver-problems.test b/tests/Composer/Test/Fixtures/installer/solver-problems.test
index 66d10f1ef..6b9c03630 100644
--- a/tests/Composer/Test/Fixtures/installer/solver-problems.test
+++ b/tests/Composer/Test/Fixtures/installer/solver-problems.test
@@ -119,7 +119,7 @@ Your requirements could not be resolved to an installable set of packages.
   Problem 6
     - Root composer.json requires linked library lib-icu 1001.* but it has the wrong version installed, try upgrading the intl extension.
   Problem 7
-    - Root composer.json requires PHP extension ext-xml 1002.* but it has the wrong version (%s) installed. Install or enable PHP's xml extension.
+    - Root composer.json requires PHP extension ext-xml 1002.* but it has the wrong version installed (%s).
   Problem 8
     - Root composer.json requires php 1 but your php version (%s) does not satisfy that requirement.
   Problem 9
@@ -161,4 +161,3 @@ Alternatively, you can run Composer with `--ignore-platform-req=ext-xml` to temp
 Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
 
 --EXPECT--
-
diff --git a/tests/Composer/Test/Fixtures/installer/update-ignore-platform-package-requirement-list-upper-bounds.test b/tests/Composer/Test/Fixtures/installer/update-ignore-platform-package-requirement-list-upper-bounds.test
new file mode 100644
index 000000000..0c7e776de
--- /dev/null
+++ b/tests/Composer/Test/Fixtures/installer/update-ignore-platform-package-requirement-list-upper-bounds.test
@@ -0,0 +1,50 @@
+--TEST--
+Update with ignore-platform-req list ignoring upper bound of a dependency
+--COMPOSER--
+{
+    "repositories": [
+        {
+            "type": "package",
+            "package": [
+                { "name": "a/a", "version": "1.0.1", "require": { "ext-foo-bar": "3.*" } },
+                { "name": "b/b", "version": "1.0.1", "require": { "ext-foo-bar": "10.*" } }
+            ]
+        }
+    ],
+    "require": {
+        "a/a": "1.0.*",
+        "b/b": "1.0.*",
+        "php": "^4.3",
+        "ext-foo-baz": "9.0.0"
+    },
+    "provide": {
+        "ext-foo-bar": "5.0.3"
+    }
+}
+--INSTALLED--
+[
+    { "name": "a/a", "version": "1.0.0" }
+]
+--RUN--
+update --ignore-platform-req=php+ --ignore-platform-req=ext-foo-bar+ --ignore-platform-req=ext-foo-baz+
+
+--EXPECT-EXIT-CODE--
+2
+
+--EXPECT-OUTPUT--
+Loading composer repositories with package information
+Updating dependencies
+Your requirements could not be resolved to an installable set of packages.
+
+  Problem 1
+    - Root composer.json requires PHP extension ext-foo-baz [== 9.0.0.0 || >= 9.0.0.0] but it is missing from your system. Install or enable PHP's foo-baz extension.
+  Problem 2
+    - Root composer.json requires b/b 1.0.* -> satisfiable by b/b[1.0.1].
+    - b/b 1.0.1 requires ext-foo-bar 10.* -> it has the wrong version installed (5.0.3 provided by __root__ 1.0.0+no-version-set).
+
+To enable extensions, verify that they are enabled in your .ini files:
+__inilist__
+You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode.
+Alternatively, you can run Composer with `--ignore-platform-req=ext-foo-baz --ignore-platform-req=ext-foo-bar` to temporarily ignore these required extensions.
+
+--EXPECT--
diff --git a/tests/deprecations-8.1.json b/tests/deprecations-8.1.json
index 0982624a2..50fe04397 100644
--- a/tests/deprecations-8.1.json
+++ b/tests/deprecations-8.1.json
@@ -77,12 +77,12 @@
     {
         "location": "Composer\\Test\\InstallerTest::testIntegrationWithRawPool",
         "message": "preg_match(): Passing null to parameter #4 ($flags) of type int is deprecated",
-        "count": 1800
+        "count": 1820
     },
     {
         "location": "Composer\\Test\\InstallerTest::testIntegrationWithPoolOptimizer",
         "message": "preg_match(): Passing null to parameter #4 ($flags) of type int is deprecated",
-        "count": 1800
+        "count": 1820
     },
     {
         "location": "Composer\\Test\\Package\\Archiver\\ArchivableFilesFinderTest::testManualExcludes",