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    preg_last_error

    (PHP 5 >= 5.2.0, PHP 7, PHP 8)

    preg_last_error — 直近の PCRE 正規表現処理のエラーコードを返す

    説明

    preg_last_error(): int

    直近の PCRE 正規表現処理のエラーコードを返します。

    例1 preg_last_error() の例

    <?php

    preg_match    ('/(?:\D+|<\d+>)*[!?]/', 'foobar foobar foobar');

    if (    preg_last_error() == PREG_BACKTRACK_LIMIT_ERROR) {
    echo     'Backtrack limit was exhausted!';
    }

    ?>

    上の例の出力は以下となります。

    Backtrack limit was exhausted!

    パラメータ

    この関数にはパラメータはありません。

    参考

    • preg_last_error_msg() - 最後に実行した PCRE 正規表現に関するエラーメッセージを返す

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    User Contributed Notes 10 notes

    up
    5
    nicoSWD
    4 years ago
    PHP 8 has a native function to retrieve the actual error message, so these helper functions are no longer necessary.

    https://www.php.net/preg_last_error_msg

    <?php

    preg_match    ('/(?:\D+|<\d+>)*[!?]/', 'foobar foobar foobar');

    if (    preg_last_error() !== PREG_NO_ERROR) {
    echo     preg_last_error_msg(); // Prints "Backtrack limit exhausted"
    }

    ?>
    up
    13
    gk at anuary dot com
    10 years ago
    In PHP 5.5 and above, getting the error message is as simple as:

    <?php
    echo array_flip(get_defined_constants(true)['pcre'])[preg_last_error()];
    up
    8
    andre at koethur dot de
    11 years ago
    Here is a more advanced function to convert an error code to text:

    <?php

    function preg_errtxt($errcode)
    {
    static     $errtext;

    if (!isset(    $errtxt))
    {
    $errtext = array();
    $constants = get_defined_constants(true);
    foreach (    $constants['pcre'] as $c => $n) if (preg_match('/_ERROR$/', $c)) $errtext[$n] = $c;
    }

    return     array_key_exists($errcode, $errtext)? $errtext[$errcode] : NULL;
    }

    ?>
    up
    4
    Daniel Klein
    5 years ago
    Here is a correction to one of the previous "get error message" snippets. It filters out the non-error codes which stops "Warning: array_flip(): Can only flip STRING and INTEGER values!" from being emitted due to ["PCRE_JIT_SUPPORT"]=>bool(true):

    <?php
    echo array_flip(array_filter(get_defined_constants(true)['pcre'], function ($value) {
    return     substr($value, -6) === '_ERROR';
    },     ARRAY_FILTER_USE_KEY))[preg_last_error()];
    up
    1
    Anonymous
    5 years ago
    If you use T-Regx library, to get the last constant, you can use

    <?php

    echo preg_last_error_constant(); // 'PREG_BAD_UTF8_ERROR'
    up
    2
    johan at bluemoonit dot net
    14 years ago
    The above function pcre_error_deocde [sic] is not correct - not all of the used constants are errors constants. For example, when the error is actually PREG_BAD_UTF8_ERROR, the function outputs the text for PREG_SPLIT_OFFSET_CAPTURE.
    up
    1
    zerodahero at gmail dot com
    4 years ago
    In PHP 7.3+, and depending on the environment, there may be other constants that aren't ints which will cause errors with array_flip. I opted to go with a RegexException and a filter on gk's note.

    <?php

    class RegexException extends \Exception {

    public     $errorCode;

    public function     __construct(
    int $errorCode,
    string $additionalMessage = null
    ) {
    $this->errorCode = $errorCode;

    $errorMessage = $this->getErrorString($errorCode) ?? 'Unknown regex error';
    $additionalMessage = $additionalMessage ? " $additionalMessage" : '';

    parent::__construct("Regex error thrown: $errorMessage." . $additionalMessage);
    }

    /**
    * Gets an error string (const name) for the PCRE error code
    *
    * @param int $errorCode
    *
    * @return string|null
    */
    private function getErrorString(int $errorCode): ?string
    {
    $pcreConstants = get_defined_constants(true)['pcre'] ?? [];

    /*
    * NOTE: preg_last_error() returns an int, but there are constants
    * in PHP 7.3+ that are strings, bools, or otherwise. We can pretty
    * safely filter out the non-integers to fetch the appropriate
    * error constant name.
    */
    $pcreConstants = array_filter($pcreConstants, function ($code) {
    return     is_int($code);
    });

    $errorStrings = array_flip($pcreConstants);

    return     $errorStrings[$errorCode] ?? null;
    }

    Usage:

    throw new     RegexException(preg_last_error());
    up
    0
    eu at ericruiz dot com dot br
    7 years ago
    Take it into account before use this function.

    My php --version
    PHP 5.6.29 (cli) (built: Dec 8 2016 09:19:46)
    Copyright (c) 1997-2016 The PHP Group
    Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies

    On Linux Fedora 23 4.8.13-100.fc23.x86_64 #1 SMP Fri Dec 9 14:51:40 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

    <?php
    // @see http://stackoverflow.com/questions/4440626/how-can-i-validate-regex

    // returns true because there is no opening "(" for the closing ")"
    var_dump(preg_match('~InvalidRegular)Expression~', null) === false);

    // this SHOULD be something different from 0, but...
    var_dump(preg_last_error());
    ?>
    up
    0
    andre at koethur dot de
    11 years ago
    Just an addition to my previous note: In unicode mode (with "u" modifier), PREG_BAD_UTF8_ERROR only reflects errors in the subject string. If the pattern itself contains invalid characters, preg_match() (or preg_match_all()) returns false but preg_last_error() returns 0 indicating PREG_NO_ERROR. Instead, php issues a warning: "preg_match(): Compilation failed: invalid UTF-8 string at offset 0"
    up
    -1
    Vladimir Valikaev
    5 years ago
    Getting error as text (small update):

    <?php
    echo array_flip(array_filter(get_defined_constants(true)['pcre'], function($v) { return is_integer($v); }))[preg_last_error()];
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