Can anyone explain the following regex?

Thank you!
HOw about:

'/\s{2,}/'

break it down part by part:

/ - opening delimiter
[ - group of characters
\n - new line
\r - carriage return
\t - tab character
] - close group
+ - one or more of characters matching any character in the group
/ - closing delimiter

HTH

'/\s{2,}/' Finds spaces in groups of 2 or more (ie: whenver there are two  spaces  between  a  word  instead of one like normal)

Ok last question in the next phrase:
preg_replace('/(<a[^>]*>)(<img[^>]+alt=")([^"]*)("[^>]*>)(<\/a>)/i', '$1$3$5<br />', $buffer);

what is the '$1$3$5' pharse mean?

Well lets look at the regex first:

/(<a[^>]*>)(<img[^>]+alt=")([^"]*)("[^>]*>)(<\/a>)/i
/ Opening delimiter
( creates first match grouping
<a[^>]*> matches any anchor opening tag
) closes first grouping
( creates second grouping
<img[^>]+alt=" matches any img tag up to the alt attribute
) closes second grouping
( creates third grouping
[^"]* matches the characters found within the alt attribute
) closes third group
( creates fourth grouping
"[^>]*> matches the remainder of the img tag
) closes fourth grouping
( creates fifth grouping
<\/a> matches a closing anchor tag
) closes fifth grouping
/i makes all matches case insensitive

Then there is the replace with part:
$1$3$5<br />
dollar sign number is a back reference, refering the that's numbers equivalent group in the matching phrase. So...
$1 would be the opening anchor tag
$3 would be the alt attribute in the img tag
$5 would be the closing anchor tag

geex you know regex!
Thank you!

Im trying to add the following regex:
to replace a stylesheet and I get an error I cant see the syntax problem do you?
I can open a new question if you like

$buffer = preg_replace =('/<link[^>]+rel="[^"]*stylesheet"[^>]*/','<link href="mobile.css" rel="stylesheet" type="text/css"/>',$buffer)

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What's the error?

Parse error: syntax error, unexpected '='

haha didn't even notice...

$buffer = preg_replace =('/<link[^>]+rel="[^"]*stylesheet"[^>]*/','<link href="mobile.css" rel="stylesheet" type="text/css"/>',$buffer);

should be

$buffer = preg_replace('/<link[^>]+rel="[^"]*stylesheet"[^>]*/','<link href="mobile.css" rel="stylesheet" type="text/css"/>',$buffer);

preg_replace is a function call and should be followed by a (

oh god whats wrong with ???sorry I dont know how i ddit notice that

Also for the results you are desiring you should use:

$buffer = preg_replace('/<link[^>]+rel="[^"]*stylesheet"[^>]*/','<link href="mobile.css" rel="stylesheet" type="text/css"/',$buffer);

Your's left an extra > after the link tag because you aren't matching for the final > but you are including a closing > in the replacement.

What is the meaning of this sign alone ^ in a regex?

^ means not including so...
[^>] means all characters not including greater than.

Im tryng to create a regex that will remove all the character between a certain div
for exmp:

<div id="banner">
remove
remove

</div>

I tried:
$buffer = preg_replace('/(<div+id="banner".*.<\/div>/','', $buffer);

but its not working

Well first thing about preg_replace is that you can use your own delimiter, I like to use something that won't be present in my regx. Second you're not allowing for white space between <div and id= Try this: (also feel free to make another question, and I'll answer there if this doesn't work (cause I'm greedy for points! lol))

$banner = '#' // Opening delimiter
.'<div'   // opening of div
.'(.*)' // any character within the div tag
.'id="banner"' // with specific ID of banner
.'(.*)' // any character after id of the div and the closing div
.'</div>' // the closing div tag
.'#'; // closing delmiter
$buffer = preg_replace($banner,'', $buffer);

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Note I only wrote it that way to separate out the parts of the regex. This is something I learned on EE from Ray_Paseur and its something I do now because it greatly improves how easy it is to understand what you are doing. Also Note: this will not work if there is a nested div in the banner div (because it will cut off at the first closing div).

HTH

$banner = '#'	// Opening delimiter
.'<div'		// opening of div
.'([^>]+)'	// any character within the div tag
.'id="banner"'	// with specific ID of banner
.'([^>]+)'	// any character after id of the div before the closing of the div tag
.'>'		// closing of the div tag
.'(.*)'		// any character within the DIV
.'</div>'	// closing of the  div
.'#';		// closing delmiter
$buffer = preg_replace($banner,'', $buffer);

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Actually try that... so it doesn't match the first opening of any div until the last closing div... maybe...

Can you write in in thus format please:$buffer = preg_replace('/(<div+id="banner".*.<\/div>/','', $buffer)

I tried the first one its not working I have to add somehing for the spaces though,
here is the new question,
https://www.experts-exchange.com/questions/27412639/regex-ancor-a-text-between-divs.html

$buffer = preg_replace('#<div([^>]+)id="banner"([^>]+)>(.*)</div>#','', $buffer);

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ok find it:

$buffer = preg_replace('/<div([^>]+)id="banner">(.*?)<\/div>/s','test', $buffer); is working
not really sure how to explain it what is the diffrence between (.*?) and (.*)

oh posted it in the wrong question sorry