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# preg_match

(PHP 3 >= 3.0.9, PHP 4, PHP 5)

preg_match -- Perform a regular expression match

## Descrição

int preg_match ( string pattern, string subject [, array &matches [, int flags [, int offset]]] )

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 the following flag:

  `PREG_OFFSET_CAPTURE`

    If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the return value in 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`.

`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.

  > 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 irá imprimir:

  >     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
  >             )

  >     )

## Valores de retornado

preg_match() returns the number of times `pattern` matches. That will be either 0 times (no match) or 1 time because preg_match() will stop searching after the first match. preg_match_all() on the contrary will continue until it reaches the end of `subject`. preg_match() returns `FALSE` if an error occurred.

## Histórico

Versão | Descrição
--- | ---
4.3.3 | The `offset` parameter was added
4.3.0 | The `PREG_OFFSET_CAPTURE` flag was added
4.3.0 | The `flags` parameter was added

## 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 /* The \b in the pattern indicates a word boundary, so only the distinct * word "web" is matched, and not a word partial like "webbing" or "cobweb" */ 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 irá imprimir:
    domain name is: php.net

## Notas

> Dica: Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() or strstr() instead as they will be faster.

## Veja também

preg_match_all()
preg_replace()
preg_split()

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