Page 594 - Beginning PHP 5.3

Part III: Using PHP in Practice
Searching Arrays with preg_grep()

preg_match() and preg_match_all() search individual strings of text. If you want to search an entire
array of strings, you can use preg_grep() . This function takes three arguments — the regular
expression, the array of strings, and optional flags — and returns an array containing the array elements
that matched the expression, keyed by the elements ’ indices in the original array. Here ’ s an example:

$text = array(
“His three whales are as good whales as were ever published in”,
“Wapping, at any rate; and his stump as unquestionable a stump”,
“as any you will find in the western clearings.”
);

$results = preg_grep( “/\bin\b/”, $text );
echo “ < pre > ”;
print_r( $results );
echo “ < /pre > ”;

This code searches for the word “ in ” within the strings in the $text array, and produces the
following output:

Array
(
[0] = > His three whales are as good whales as were ever published in
[2] = > as any you will find in the western clearings.

)
If you ’ d prefer to get a list of elements that don ’ t match the pattern, pass the PREG_GREP_INVERT flag as
the third argument to preg_grep() :

$text = array(
“His three whales are as good whales as were ever published in”,
“Wapping, at any rate; and his stump as unquestionable a stump”,
“as any you will find in the western clearings.”
);

$results = preg_grep( “/\bin\b/”, $text, PREG_GREP_INVERT );
echo “ < pre > ”;
print_r( $results );

echo “ < /pre > ”;
This code displays:
Array
(
[1] = > Wapping, at any rate; and his stump as unquestionable a stump

)
preg_grep() doesn ’ t give you much detail, such as the actual matched text or how many times the text
matched, but it ’ s great for quickly reducing a large array of text strings — such as that returned from a
database query — down to just the strings that match. You can then perform a more fine - grained search
on the matched strings, if required.

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