问题
I'm having a problem trying to ignore whitespace in-between certain characters. I've been Googling around for a few days and can't seem to find the right solution.
Here's my code:
// Get Image data
preg_match('#<a href="(.*?)" title="(.*?)"><img alt="(.*?)" src="(.*?)"[\s*]width="150"[\s*]height="(.*?)"></a>#', $data, $imagematch);
$image = $imagematch[4];
Basically these are some of the scenarios I have:
<a href="/wiki/File:Sky1.png" title="File:Sky1.png"><img alt="Sky1.png" src="http://media-mcw.cursecdn.com/thumb/5/56/Sky1.png/150px-Sky1.png"width="150" height="84"></a>
(Notice the lack of a space between width="" and src="")
And
<a href="/wiki/File:TallGrass.gif" title="File:TallGrass.gif"><img alt="TallGrass.gif" src="http://media-mcw.cursecdn.com/3/34/TallGrass.gif" width="150"height="150"></a>
(Notice the lack of a space in between width="" and height="".)
Is there anyway to ignore the whitespace in between those characters? As I am not a Regex expert.
回答1:
Add a \s? if a space can be allowed.
\s stands for white space
? says the preceding character may occur once or not occur.
If more than one spaces are allowed and is optional, use \s*.
* says preceding character can occur zero or more times.
'#<a href\s?="(.*?)" title\s?="(.*?)"><img alt\s?="(.*?)" src\s?="(.*?)"[\s*]width\s?="150"[\s*]height\s?="(.*?)"></a>#'
allows an optional space between attribute name and =.
If you want an optional space after the = also, add a \s? after it also.
Likewise, wherever you have optional characters, you can use ? if the maximum occurrence is 1 or * if the maximum occurrence is unlimited, following the optional character.
And your actual problem was [\s*] which causes occurrence of a whitespace or a * as characters enclosed in [ and ] is a character class. A character class allows occurrence of any of its members once (so remove * from it) and if you append a quantifier (?, +, * etc) after the ] any character(s) in the character class can occur according to the quantifier.
来源：https://stackoverflow.com/questions/14293024/optional-whitespace-regex