What does isU of preg_match in php mean?

i: means in-casesensitive, that is, case-insensitive
s: PCRE_DOTALL, means that the dot can match newline characters.
U: means PCRE_UNGREEDY, which means non-greedy, equivalent to .*? in perl/python language. During the matching process, for .* regular rules, they will be executed immediately as soon as there is a match, instead of waiting.* All characters are consumed and then rolled back one by one.

Example

preg_match compatibleRegular expressionIn the syntax, b represents the word boundary

So: The following should be OK? ? ?

$a="test,admin,abc";
$b="te";
$exist=preg_match("/b{$b}b/",$a);
if($exist)
{
echo "存在";
}else
{
echo "不存在";
}

Look at the relevant instructions

The code is as follows:

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

preg_match() returns the number of times pattern is matched. Either 0 times (no match) or 1 time, since preg_match() will stop searching after the first match. preg_match_all(), on the contrary, will search until the end of subject. preg_match() returns false on error.

Example:

<?php
$a = "abcdefgabcdefaaag";
preg_match(&#39;|abc([a-z]+)g|isu&#39;,$a,$out1);
preg_match_all(&#39;|abc([s]+)g|isu&#39;,$a,$out2);
echo "<pre class="brush:php;toolbar:false">";
print_r($out1);
print_r($out2);
echo "

"; ?>

Writing:

The difference between using double quotes and single quotes

<?php
preg_match_all("/href="(.*)"/isu",$contents,$out);
preg_match_all(&#39;|href="(.*)"|isu&#39;,$contents,$out);
?>

The above is the detailed content of What does isU of preg_match in php mean?. For more information, please follow other related articles on the PHP Chinese website!