Как найти число символов в строке

Example:

<?php
// the Arabic (Hello) string below is: 59 bytes and 32 characters
$utf8 = "السلام علیکم ورحمة الله وبرکاته!";var_export( strlen($utf8) ); // 59
echo "<br>";
var_export( mb_strlen($utf8, 'utf8') ); // 32
?>

<?php
// PHP < 8.0
if (!strlen($text)) {
  echo 'Blank';
}// PHP >= 8.0
if ($text === null || $text === '')) {
  echo 'empty';
}

There are three possible situations:

1. Most likely case: the database column is UTF-8 with a length defined in unicode code points (e.g. mysql varchar(200) for a utf-8 database).

<?php
// ok if php.ini default_charset set to UTF-8 (= default value)
mb_strlen($value);
iconv_strlen($value);
// always ok
mb_strlen($value, "UTF-8");
iconv_strlen($value, "UTF-8");// BAD, do not use:
strlen(utf8_decode($value)); // breaks for some multi-byte characters
grapheme_strlen($value); // counts graphemes, not code points
?>

2. The database column has a length defined in bytes (e.g. oracle's VARCHAR2(200 BYTE))

<?php
// ok, but assumes mbstring.func_overload is 0 in php.ini (= default value)
strlen($value);
// ok, forces count in bytes
mb_strlen($value, "8bit")
?>

3. The database column is in another character set (UTF-16, ISO-8859-1, etc...) with a length defined in characters / code points.

Find the character set used, and pass it explicitly to the length function.

<?php
// ok, supported charsets: http://php.net/manual/en/mbstring.supported-encodings.php
mb_strlen($value, $charset);
// ok, supported charsets: https://www.gnu.org/software/libiconv/
iconv_strlen($value, $charset);
?>

In PHP, a null byte in a string does NOT count as the end of the string, and any null bytes are included in the length of the string.

For example, in PHP:

strlen( "test" ) = 5

In C, the same call would return 2.

Thus, PHP's strlen function can be used to find the number of bytes in a binary string (for example, binary data returned by base64_decode).

<?php

$attributes

= array('one', 'two', 'three');

if (

strlen($attributes) == 0 && !is_bool($attributes)) {
    echo "We are in the 'if'n";  //  PHP 5.3
} else {
    echo "We are in the 'else'n";  //  PHP 5.2
}?>

This is because in 5.2 strlen will automatically cast anything passed to it as a string, and casting an array to a string yields the string "Array".  In 5.3, this changed, as noted in the following point in the backward incompatible changes in 5.3 (http://www.php.net/manual/en/migration53.incompatible.php):

"The newer internal parameter parsing API has been applied across all the extensions bundled with PHP 5.3.x. This parameter parsing API causes functions to return NULL when passed incompatible parameters. There are some exceptions to this rule, such as the get_class() function, which will continue to return FALSE on error."

So, in PHP 5.3, strlen($attributes) returns NULL, while in PHP 5.2, strlen($attributes) returns the integer 5.  This likely affects other functions, so if you are getting different behaviors or new bugs suddenly, check if you have upgraded to 5.3 (which we did recently), and then check for some warnings in your logs like this:

strlen() expects parameter 1 to be string, array given in /var/www/sis/lib/functions/advanced_search_lib.php on line 1028

If so, then you are likely experiencing this changed behavior.

<?php
$foo = null;
$len = strlen(null);
$bar = '';

echo

"Length: " . strlen($foo) . "<br>";
echo "Length: $len <br>";
echo "Length: " . strlen(null) . "<br>";

if (

strlen($foo) === 0) echo 'Null length is Zero <br>';
if ($len === 0) echo 'Null length is still Zero <br>';

if (

strlen($foo) == 0 && !is_null($foo)) echo '!is_null(): $foo is truly an empty string <br>';
else echo '!is_null(): $foo is probably null <br>';

if (

strlen($foo) == 0 && isset($foo)) echo 'isset(): $foo is truly an empty string <br>';
else echo 'isset(): $foo is probably null <br>';

if (

strlen($bar) == 0 && !is_null($bar)) echo '!is_null(): $bar is truly an empty string <br>';
else echo '!is_null(): $foo is probably null <br>';

if (

strlen($bar) == 0 && isset($bar)) echo 'isset(): $bar is truly an empty string <br>';
else echo 'isset(): $foo is probably null <br>';
?>

// Begin Output:
Length: 0
Length: 0
Length: 0

Null length is Zero
Null length is still Zero

!is_null(): $foo is probably null
isset(): $foo is probably null

!is_null(): $bar is truly an empty string
isset(): $bar is truly an empty string
// End Output

So it would seem you need either is_null() or isset() in addition to strlen() if you care whether or not the original value was null.

I created a 20,00,000 byte string (~20 megabytes), and iterated ONE HUNDRED MILLION TIMES in a loop. Every loop iteration did a new strlen() on that very, very long string.

The result: 100 million strlen() calls on a 20 megabyte string only took a total of 488 milliseconds. And the strlen() calls didn't get slower/faster even if I made the string smaller or bigger. The strlen() was pretty much a constant-time, super-fast operation

So either PHP7 stores the length of every string as a field that it can simply always look up without having to count characters. Or it caches the result of strlen() until the string contents actually change. Either way, you should now never, EVER worry about strlen() performance again. As of PHP7, it is super fast!

Here is the complete benchmark code if you want to reproduce it on your machine:

<?php

$iterations

= 100000000; // 100 million
$str = str_repeat( '0', 20000000 );// benchmark loop and variable assignment to calculate loop overhead
$start = microtime(true);
for( $i = 0; $i < $iterations; ++$i ) {
    $len = 0;
}
$end = microtime(true);
$loop_elapsed = 1000 * ($end - $start);// benchmark strlen in a loop
$len = 0;
$start = microtime(true);
for( $i = 0; $i < $iterations; ++$i ) {
    $len = strlen( $str );
}
$end = microtime(true);
$strlen_elapsed = 1000 * ($end - $start);// subtract loop overhead from strlen() speed calculation
$strlen_elapsed -= $loop_elapsed;

echo

"nstring length: {$len}ntest took: {$strlen_elapsed} millisecondsn";?>