Are regex's allowed in PHP switch/case statements and how to use them ?
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2can you clarify this by giving an example of what you are trying to accomplish?– AdamCommented Oct 28, 2010 at 14:16
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4 Answers
Switch-case statement works like if-elseif.
As well as you can use regex for if-elseif, you can also use it in switch-case.
if (preg_match('/John.*/', $name)) {
// do stuff for people whose name is John, Johnny, ...
}
can be coded as:
switch $name {
case (preg_match('/John.*/', $name) ? true : false) :
// do stuff for people whose name is John, Johnny, ...
break;
}
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14This only works when
$nameevaluates totrue. If$name == ''this will yield wrong results. -1– NikiCCommented Oct 29, 2010 at 13:19 -
9@nikic: you're right but this answers the OP's question :
Are regex's allowed in PHP switch/case statements and how to use them ?– bourbakiCommented Oct 29, 2010 at 18:26 -
2Took me a while to understand why this works. And I think it is an ugly hack. The key is that "most" strings validate to true. And the answer to the question would be: it works, most of the times.– EzequielCommented May 31, 2013 at 15:36
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switch $name { case (preg_match('/e*/', $name)): echo "match";break;} shouldn't work correctly for $name = "" because preg_match('/e*', $name) is true but true != "".– EzequielCommented May 31, 2013 at 15:38
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2The
preg_match()statement incasein the answer can be simplified ascase (!!preg_match('/John.*/', $name)):Commented Jun 30, 2018 at 23:07
No or only limited. You could for example switch for true:
switch (true) {
case $a == 'A':
break;
case preg_match('~~', $a):
break;
}
This basically gives you an if-elseif-else statement chain, but with syntax and might of switch (for example fall-through.)
Yes, but you should use this technique to avoid issues when the switch argument evals to false:
switch ($name) {
case preg_match('/John.*/', $name) ? $name : !$name:
// do stuff
}
answered Oct 28, 2010 at 14:18
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Thanks for your response. If i understand well, i can do
preg_match("/regex/", $foo) ? true : false;. Can't I ?– TotoCommented Oct 28, 2010 at 15:23 -
1The first example in this answer is better than all the other answers because it will always correctly match (or not) the subject of the
switch(), whereas returning true or false from thepreg_match()ternary could have unexpected results, as in @NikiC's empty string example.– MichaelCommented Oct 24, 2011 at 7:43
Keep in mind the above answer can be slightly optimized like this:
Changing:
switch $name {
case (preg_match('/John.*/', $name) ? true : false) :
// do stuff for people whose name is John, Johnny, ...
break;
}
To:
switch $name {
case (bool)preg_match('/John.*/', $name) :
// do stuff for people whose name is John, Johnny, ...
break;
}
