Substr help

[Supertrooper]

Hello,

 

Ok, so I am passing something through via a web form and I want to check if the first 2 letters contain something so I have worked out you can do:

 

if (substr($foobar, 0, 2) === 'ab')

 

{ echo "blah blah"; }

 

What happens if I want to check if the first two letters are ab or ba?

 

I thought I could do

 

 

if (substr($foobar, 0, 2) === 'ab' or 'ba')

 

{ echo "blah blah"; }

 

but this doesn't seem to work.

 

Also, what if I want to check for all variants of CAPS for example, AB, ab, Ab, bA etc?

 

Thanks

[Christian F.]

For this you'd want to use Regular Expressions:

if (preg_match ('/^(?:ab|ba)/i', $string)) {
    // String starts with ab or ba, case insensitive.
}

 

PS: Please use the

tags around code you post here. It makes both the code, and your post, a lot easier to read. Thanks.

[rythemton]

Your second bit of code doesn't work the way you think it does:

if (substr($foobar, 0, 2) === 'ab' or 'ba') // This won't work right

This is going to check if the first two characters is 'ab', then it's going to check to see if 'ba' is TRUE or FALSE, which will be always TRUE because a nonempty string is considered TRUE in PHP. So you can see this better, here is your code again using parenthesis to show order of precedence:

if ( ( substr($foobar, 0, 2) === 'ab' ) or ( 'ba' ) ) 

You'll need to do the comparison twice for it to work right:

if (substr($foobar, 0, 2) === 'ab' or substr($foobar, 0, 2) === 'ba') 

 

As for checking variation in Caps, there are many ways you could go. One of the easiest in this case would be to force the results to be lowercase:

if (strtolower(substr($foobar, 0, 2)) === 'ab' or strtolower(substr($foobar, 0, 2)) === 'ba') 

 

You can see more of PHP order of precedence at http://php.net/manual/en/language.operators.precedence.php

 

For more complicated checks, you can also use regular expressions, which can shorten your code.

[Supertrooper]

OK thanks guys.