How do I use PHP string interpolation and square brackets in a MySQL regexp?

Question

In my query I have:

$search .= "and title REGEXP '[[:<:]]$q[[:>:]]' ";

Which produces the following error in the Apache error log:

PHP Parse error:  syntax error, unexpected '[', expecting identifier (T_STRING) or variable (T_VARIABLE) or number (T_NUM_STRING)

I tried putting {} around it, but that didn't work either.

Thank you.

Escape the dollar sign with a backslash. PHP is trying to interpret it as a variable. Or better yet, use a prepared statement and you don't have to worry about these things. — miken32
– miken32, Commented Aug 3, 2016 at 22:35
Prepared statements are imperative here. This is asking for serious problems. — tadman
– tadman, Commented Aug 3, 2016 at 22:42
I solved it by using this code prior to the actual query: $regexpVariable = "[[:<:]]" . $q . "[[:>:]]"; — PioneerMan
– PioneerMan, Commented Aug 3, 2016 at 23:24
@NestMan Look at what a tool like this can do to your site if you make a mistake of this magnitude. It's not a good list of things. — tadman
– tadman, Commented Aug 3, 2016 at 23:52

Rick James · Accepted Answer · 2016-08-04 01:26:24Z

2

Add braces: $search .= "and title REGEXP '[[:<:]]{$q}[[:>:]]'"; -- otherwise it thinks you are referencing the $q array.

PHP allows array lookups in strings, such as "... $q[...] ..." It also allows expresssions: "... {$a+$b} ..." if you add the braces. Putting those together solves this problem.

answered Aug 4, 2016 at 1:26

Rick James

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