steamngn
asked on
PHP regex expression to capture and replace part of string
Say I have a string and within that string are multiple occurrences of a string similar to "@41|8:00|10/01/2015@".
What I need to do is find each of these strings and remove everything between the two "|" so "@41|8:00|10/01/2015@" needs to become "@41|10/01/2015@".
I can find and replace the entire string with
I just cannot get my head around the expression...
Andy
What I need to do is find each of these strings and remove everything between the two "|" so "@41|8:00|10/01/2015@" needs to become "@41|10/01/2015@".
I can find and replace the entire string with
preg_replace('/@[^>]*@/', 'replaced', $teststr);I just cannot get my head around the expression...
Andy
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ASKER
excellent!
Expression Explained
/(@\d+)\|.*?\|(.*?@)/
(@\d+) - match anything that starts with a '@' followed by one or more digits (\d). The ( ) around the expression means we want to save it as a parameter so that we can use it in the replace
\| - | is a special char in regex (means or) - so we have to escape it with a '\' - we don't need it because we will recreate it in the replace.
.*? - no ( ) because we are not interested in this bit. the .* says match anything the ? says don't be greedy.
.* will match anything which would include the next \| - however we want it to stop matching when it hits the \| so we put a ? after the .* to say don't be greedy take only what you can up until the next thing we are looking for - in this case the \|
\| - the next | delimiter
(.*?@) - the ( ) says keep this for use in the replace (this will be parameter #2) - says match anything but don't be greedy (?) until you hit a @ - include that in the match and then stop.
Why do we not put a ? (don't be greedy) after the \d+ in the first match?
Answer: we could but it is not necessary. The \d specifier only matches 0-9 - so as soon as it hits a non digit it stops anyway.
What do the opening and closing '/' mean
Answer: they are just regular expression delimiters saying where it starts and where stops.
Now for the replace - easy
\1|\2
\1 means the first saved match - (@\d+)
| - insert a | - we don't need to escape it because in the replace string the | character is just a |
\2 - the second matched parameter (.*?@)
/(@\d+)\|.*?\|(.*?@)/
(@\d+) - match anything that starts with a '@' followed by one or more digits (\d). The ( ) around the expression means we want to save it as a parameter so that we can use it in the replace
\| - | is a special char in regex (means or) - so we have to escape it with a '\' - we don't need it because we will recreate it in the replace.
.*? - no ( ) because we are not interested in this bit. the .* says match anything the ? says don't be greedy.
.* will match anything which would include the next \| - however we want it to stop matching when it hits the \| so we put a ? after the .* to say don't be greedy take only what you can up until the next thing we are looking for - in this case the \|
\| - the next | delimiter
(.*?@) - the ( ) says keep this for use in the replace (this will be parameter #2) - says match anything but don't be greedy (?) until you hit a @ - include that in the match and then stop.
Why do we not put a ? (don't be greedy) after the \d+ in the first match?
Answer: we could but it is not necessary. The \d specifier only matches 0-9 - so as soon as it hits a non digit it stops anyway.
What do the opening and closing '/' mean
Answer: they are just regular expression delimiters saying where it starts and where stops.
Now for the replace - easy
\1|\2
\1 means the first saved match - (@\d+)
| - insert a | - we don't need to escape it because in the replace string the | character is just a |
\2 - the second matched parameter (.*?@)
You are welcome.
ASKER
Julian,
I went round and round ALL DAY on this.... and now with your insight I see where I was going wrong!
Excellent help, Thank you
Andy
I went round and round ALL DAY on this.... and now with your insight I see where I was going wrong!
Excellent help, Thank you
Andy
Again you are welcome Andy - glad I could be of assistence.
ASKER
Right on the money! Ok, without taking up your entire day can you break this out a bit and explain it to me? I fought with this all day and you hit it out of the park first pitch<insanely jealous></insanely jealous>
Andy