regex - How can I get at the matches when using preg_replace in PHP?


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I am trying to grab the capital letters of a couple of words and wrap them in span tags. I am using preg_replace for extract and wrapping purposes, but it's not outputting anything.

preg_replace("/[A-Z]/", "<span class=\"initial\">$1</span>", $str)

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    You need to put the pattern in parentheses /([A-Z])/, like this:

    preg_replace("/([A-Z])/", "<span class=\"initial\">$1</span>", $str)
    

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    \0 will also match the entire matched expression without doing an explicit capture using parenthesis.

    preg_replace("/[A-Z]/", "<span class=\"initial\">\\0</span>", $str)
    

    As always, you can go to php.net/preg_replace or php.net/<whatever search term> to search the documentation quickly. Quoth the documentation:

    \0 or $0 refers to the text matched by the whole pattern.


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    From the preg_replace documentation on php.net:

    replacement may contain references of the form \n or (since PHP 4.0.4) $n, with the latter form being the preferred one. Every such reference will be replaced by the text captured by the n'th parenthesized pattern.

    See Flubba's example.


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    Use parentheses around your desired capture.