How to check if a string starts with “_” in PHP? [duplicate]

Answer 1

$variable[0] != "_"

How does it work?

In PHP you can get particular character of a string with array index notation. $variable[0] is the first character of a string (if $variable is a string).

Answer 2

function starts_with($s, $prefix){
    // returns a bool
    return strpos($s, $prefix) === 0;
}

starts_with($variable, "_");

Answer 3

You might check out the substr function in php and grab the first character that way:

http://php.net/manual/en/function.substr.php

if (substr('_abcdef', 0, 1) === '_') { ... }

Answer 4

Here’s a better starts with function:

function mb_startsWith($str, $prefix, $encoding=null) {
    if (is_null($encoding)) $encoding = mb_internal_encoding();
    return mb_substr($str, 0, mb_strlen($prefix, $encoding), $encoding) === $prefix;
}

Answer 5

This is the most simple answer where you are not concerned about performance:

if (strpos($string, '_') === 0) {
    # code
}

If strpos returns 0 it means that what you were looking for begins at character 0, the start of the string.

It is documented thoroughly here: http://uk3.php.net/manual/en/function.strpos.php

(PS $string[0] === '_' is the best answer)

Answer 6

To build on pinusnegra's answer, and in response to Gumbo's comment on that answer:

function has_leading_underscore($string) {

    return $string[0] === '_';

}

Running on PHP 5.3.0, the following works and returns the expected value, even without checking if the string is at least 1 character in length:

echo has_leading_underscore('_somestring').', ';
echo has_leading_underscore('somestring').', ';
echo has_leading_underscore('').', ';
echo has_leading_underscore(null).', ';
echo has_leading_underscore(false).', ';
echo has_leading_underscore(0).', ';
echo has_leading_underscore(array('_foo', 'bar'));

/*
 * output: true, false, false, false, false, false, false
 */

I don't know how other versions of PHP will react, but if they all work, then this method is probably more efficient than the substr route.