CODEWITHSUNDEEP
phpstringtext-extractiontruncation
user188962
user188962

Reputation:

Get number in front of first occurrence of a character

I have this:

15_some_text_or_numbers;

I want to get what's in front of the first underscore. There is always a letter directly after the first underscore.

Example:

14_hello_world = 14

Result is the number 14.

Upvotes: 3

Views: 3671

Answers (4)

mickmackusa
mickmackusa

Reputation: 48011

Demos

  • I prefer sscanf() because it is explicit in its behavior -- it isolates the leading digits and casts the returned value as an integer.

    echo sscanf($string, '%d')[0];

    Or

    sscanf($string, '%d', $integer);
echo $integer;

  • Casting to an integer is an implicit operation which I also sometimes use in applications. Like sscanf(), this technique will retain the negative sign before a number as well (as a fringe consideration).

    echo (int) $string;

  • preg_replace() is a direct approach and reliable, but the output value will not be cast as an integer, capturing negative integers will require pattern adjustment, and your dev team will need a minimum understanding of regex.

    echo preg_replace('/^\d+\K.*/', '', $string);

  • preg_match() requires a very simple pattern, but creates an array before the desired string can be accessed. Negative integers must be adjusted for.

    echo preg_match('/^\d+/', $string, $m) ? $m[0] : null;

  • the following techniques rely on the existence of a known character immediately after the desired value. If there is no static character to leverage, the following will be unsuitable.

    echo strstr($string . '_', '_', true); // append an underscore to the input if not guaranteed

    And

    echo explode('_', $string, 2)[0]; // the limit parameter prevents needeless explosions

    And

    echo strtok($string, '_');

Upvotes: 0

Gordon
Gordon

Reputation: 317147

If there is always a number in front, you can use

echo (int) '14_hello_world';

See the entry on String conversion to integers in the PHP manual

Here is a version without typecasting:

$str = '14_hello_1world_12';
echo substr($str, 0, strpos($str, '_'));

Note that this will return nothing, if no underscore is found. If found, the return value will be a string, whereas the typecasted result will be an integer (not that it would matter much). If you'd rather want the entire string to be returned when no underscore exists, you can use

$str = '14_hello_1world_12';
echo str_replace(strstr($str, '_'), '', $str);

As of PHP5.3 you can also use strstr with $before_needle set to true

echo strstr('14_hello_1world_12', '_', true);

Note: As typecasting from string to integer in PHP follows a well defined and predictable behavior and this behavior follows the rules of Unix' own strtod for mixed strings, I don't see how the first approach is abusing typecasting.

Upvotes: 10

Max Shawabkeh
Max Shawabkeh

Reputation: 38643

Simpler than a regex:

$x = '14_hello_world';
$split = explode('_', $x);
echo $split[0];

Outputs 14.

Upvotes: 1

RaYell
RaYell

Reputation: 70444

preg_match('/^(\d+)/', $yourString, $matches);

$matches[1] will hold your value

Upvotes: 5

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