Question about code understanding

May I ask questions about the code understanding, could you tell me the following red code preg_match ('/[^ a-z0-9 _]/I', $ act) should be how to understand? Thank you for your help.


$ Act = Get ('Act ');
If (! Isset ($ act {0 })){
$ Act = 'Pa ';
} Elseif (preg_match ('/[^ a-z0-9 _]/I', $ act )){
Exit;
}

Reply to discussion (solution)

/[^ A-z0-9 _]/I
Match characters other than letters, numbers, and underscores

Preg_match ('/[^ a-z0-9 _]/I', $ act

Preg_match is a php regular expression matching method.
'/[^ A-z0-9 _]/I' is a matching regular expression
$ Act is a string used to check for matching

Regular Expression Description
A-z indicates that all lowercase letters are matched.
0-9 indicates matching numbers 0 ~ 9
_ Matches the underline

The entire sentence indicates whether $ act is composed of lower-case letters, numbers, or Underscores. if it is true, it is false.

Could you tell me the following red code preg_match ('/[^ a-z0-9 _]/I', $ act) How should I understand? Thank you for your help.


$ Act = Get ('Act ');
If (! Isset ($ act {0 })){
$ Act = 'Pa ';
} Elseif (preg_match ('/[^ a-z0-9 _]/I', $ act )){
Exit;
}

Thank you for your reply.

/[^ A-z0-9 _]/I
Match characters other than letters, numbers, and underscores

Thank you for your reply to fdipzone.
I basically understand the meaning of this code.
However, I have another question:

The entire sentence indicates whether $ act is composed of lower-case letters, upper-case letters, numbers, or Underscores. if it is true, otherwise it is false.
Because the regular expression is followed by/I

Is that true?

Preg_match ('/[^ a-z0-9 _]/I', $ act

Preg_match is a php regular expression matching method.
'/[^ A-z0-9 _]/I' is a matching regular expression
$ Act is a string used to check for matching

Regular Expression Description
A-z indicates that all lowercase letters are matched.
0-9 indicates matching numbers 0 ~ 9
_ Matches the underline

The entire sentence indicates whether $ act is composed of lower-case letters, numbers, or Underscores. if it is true, it is false.

Thank you for your reply.
I basically understand the meaning of this code.
However, I have another question:

The entire sentence indicates whether $ act is composed of lower-case letters, upper-case letters, numbers, or Underscores. if it is true, otherwise it is false.
Because the regular expression is followed by/I

Is that true?

If (preg_match ('/[^ a-z0-9 _]/I', $ act )){
Exit;
}
If $ act contains characters other than letters, numbers, and underscores, exit

Preg_match ('/[^ a-z0-9 _]/I', $ act

Preg_match is a php regular expression matching method.
'/[^ A-z0-9 _]/I' is a matching regular expression
$ Act is a string used to check for matching

Regular Expression Description
A-z indicates that all lowercase letters are matched.
0-9 indicates matching numbers 0 ~ 9
_ Matches the underline

The entire sentence indicates whether $ act is composed of lower-case letters, numbers, or Underscores. if it is true, it is false.

Thank you for your reply.
I basically understand the meaning of this code.
However, I have another question:

The entire sentence indicates whether $ act is composed of lower-case letters, upper-case letters, numbers, or Underscores. if it is true, otherwise it is false.
Because the regular expression is followed by/I

Is that true?

Yes.

You can find and learn simple regular expressions.