preg_match

    (PHP 4, PHP 5, PHP 7, PHP 8)

    preg_match — Perform a regular expression match

    Descrição

    preg_match(
        string$pattern,
        string$subject,
        array&$matches = null,
        int$flags = 0,
        int$offset = 0
    ): int|false

    Searches subject for a match to the regular expression given in pattern.

    Parâmetros

    pattern

    The pattern to search for, as a string.

    subject

    The input string.

    matches

    If matches is provided, then it is filled with the results of search. $matches[0] will contain the text that matched the full pattern, $matches[1] will have the text that matched the first captured parenthesized subpattern, and so on.

    flags

    flags can be a combination of the following flags:

    PREG_OFFSET_CAPTURE

    If this flag is passed, for every occurring match the appendant string offset (in bytes) will also be returned. Note that this changes the value of matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.

    <?php
    preg_match    ('/(foo)(bar)(baz)/', 'foobarbaz', $matches, PREG_OFFSET_CAPTURE);
    print_r($matches);
    ?>

    O exemplo acima produzirá:

    Array ( [0] => Array ( [0] => foobarbaz [1] => 0 ) [1] => Array ( [0] => foo [1] => 0 ) [2] => Array ( [0] => bar [1] => 3 ) [3] => Array ( [0] => baz [1] => 6 ) )
    PREG_UNMATCHED_AS_NULL

    If this flag is passed, unmatched subpatterns are reported as null; otherwise they are reported as an empty string.

    <?php
    preg_match    ('/(a)(b)*(c)/', 'ac', $matches);
    var_dump($matches);
    preg_match('/(a)(b)*(c)/', 'ac', $matches, PREG_UNMATCHED_AS_NULL);
    var_dump($matches);
    ?>

    O exemplo acima produzirá:

    array(4) { [0]=> string(2) "ac" [1]=> string(1) "a" [2]=> string(0) "" [3]=> string(1) "c" } array(4) { [0]=> string(2) "ac" [1]=> string(1) "a" [2]=> NULL [3]=> string(1) "c" }
    offset

    Normally, the search starts from the beginning of the subject string. The optional parameter offset can be used to specify the alternate place from which to start the search (in bytes).

    Nota:

    Using offset is not equivalent to passing substr($subject, $offset) to preg_match() in place of the subject string, because pattern can contain assertions such as ^, $ or (?<=x). Compare:

    <?php
    $subject     = "abcdef";
    $pattern = '/^def/';
    preg_match($pattern, $subject, $matches, PREG_OFFSET_CAPTURE, 3);
    print_r($matches);
    ?>

    O exemplo acima produzirá:

     Array ( )

    while this example

    <?php
    $subject     = "abcdef";
    $pattern = '/^def/';
    preg_match($pattern, substr($subject,3), $matches, PREG_OFFSET_CAPTURE);
    print_r($matches);
    ?>

    will produce 

     Array ( [0] => Array ( [0] => def [1] => 0 ) )

    Alternatively, to avoid using substr(), use the \G assertion rather than the ^ anchor, or the A modifier instead, both of which work with the offset parameter.

    Valor Retornado

    preg_match() returns 1 if the pattern matches given subject, 0 if it does not, ou false em caso de falha.

    Aviso

    Esta função pode retornar o valor booleano false, mas também pode retornar um valor não booleano que pode ser avaliado como false. Leia a seção sobre Booleanos para mais informações. Use o operador === para testar o valor retornado por esta função.

    Erros/Exceções

    Se o padrão de expressão regular passado não for compilado para uma expressão regular válida, um E_WARNING será emitido.

    Registro de Alterações

    VersãoDescrição
    7.2.0 The PREG_UNMATCHED_AS_NULL is now supported for the $flags parameter.

    Exemplos

    Exemplo #1 Find the string of text "php"

    <?php
    // The "i" after the pattern delimiter indicates a case-insensitive search
    if (preg_match("/php/i", "PHP is the web scripting language of choice.")) {
    echo     "A match was found.";
    } else {
    echo     "A match was not found.";
    }
    ?>

    Exemplo #2 Find the word "web"

    <?php

    if (preg_match("/\bweb\b/i", "PHP is the web scripting language of choice.")) {
    echo     "A match was found.";
    } else {
    echo     "A match was not found.";
    }

    if (    preg_match("/\bweb\b/i", "PHP is the website scripting language of choice.")) {
    echo     "A match was found.";
    } else {
    echo     "A match was not found.";
    }
    ?>

    Exemplo #3 Getting the domain name out of a URL

    <?php
    // get host name from URL
    preg_match('@^(?:http://)?([^/]+)@i',
    "http://www.php.net/index.html", $matches);
    $host = $matches[1];

    // get last two segments of host name
    preg_match('/[^.]+\.[^.]+$/', $host, $matches);
    echo     "domain name is: {$matches[0]}\n";
    ?>

    O exemplo acima produzirá:

    domain name is: php.net

    Exemplo #4 Using named subpattern

    <?php

    $str     = 'foobar: 2008';

    preg_match('/(?P<name>\w+): (?P<digit>\d+)/', $str, $matches);


    // preg_match('/(?<name>\w+): (?<digit>\d+)/', $str, $matches);

    print_r($matches);

    ?>

    O exemplo acima produzirá:

    Array ( [0] => foobar: 2008 [name] => foobar [1] => foobar [digit] => 2008 [2] => 2008 )

    Notas

    Dica

    Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() instead as it will be faster.

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