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PHP preg_replace/preg_match vs PHP str_replace

Posted by: admin November 30, 2017 Leave a comment


Can anyone give me a quick summary of the differences please?

To my mind they both do the same thing?



str_replace replaces a specific occurrence of a string, for instance “foo” will only match and replace that: “foo”. preg_replace will do regular expression matching, for instance “/f.{2}/” will match and replace “foo”, but also “fey”, “fir”, “fox”, “f12”, etc.


See for yourself:

$string = "foo fighters";
$str_replace = str_replace('foo','bar',$string);
$preg_replace = preg_replace('/f.{2}/','bar',$string);
echo 'str_replace: ' . $str_replace . ', preg_replace: ' . $preg_replace;

The output is:

str_replace: bar fighters, preg_replace: bar barhters



str_replace will just replace a fixed string with another fixed string, and it will be much faster.

The regular expression functions allow you to search for and replace with a non-fixed pattern called a regular expression. There are many “flavors” of regular expression which are mostly similar but have certain details differ; the one we are talking about here is Perl Compatible Regular Expressions (PCRE).

If they look the same to you, then you should use str_replace.


str_replace searches for pure text occurences while preg_replace for patterns.