PHP: substr - Manual

Description

string substr ( string string, int start [, int length] )

substr() returns the portion of string specified by the start and length parameters.

If start is non-negative, the returned string will start at the start'th position in string, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.

Przykład 1. Basic substr() usage


<?php

echo substr('abcdef', 1);     // bcdef

echo substr('abcdef', 1, 3);  // bcd

echo substr('abcdef', 0, 4);  // abcd

echo substr('abcdef', 0, 8);  // abcdef

echo substr('abcdef', -1, 1); // f



// Accessing single characters in a string

// can also be achived using "curly braces"

$string = 'abcdef';

echo $string{0};                 // a

echo $string{3};                 // d

echo $string{strlen($string)-1}; // f



?>

If start is negative, the returned string will start at the start'th character from the end of string.

Przykład 2. Using a negative start


<?php

$rest = substr("abcdef", -1);    // returns "f"

$rest = substr("abcdef", -2);    // returns "ef"

$rest = substr("abcdef", -3, 1); // returns "d"

?>

If length is given and is positive, the string returned will contain at most length characters beginning from start (depending on the length of string). If string is less than or equal to start characters long, FALSE will be returned.

If length is given and is negative, then that many characters will be omitted from the end of string (after the start position has been calculated when a start is negative). If start denotes a position beyond this truncation, an empty string will be returned.

Przykład 3. Using a negative length


<?php

$rest = substr("abcdef", 0, -1);  // returns "abcde"

$rest = substr("abcdef", 2, -1);  // returns "cde"

$rest = substr("abcdef", 4, -4);  // returns ""

$rest = substr("abcdef", -3, -1); // returns "de"

?>

User Contributed Notes


Add on to "Matias from Argentina" str_format_number function.

Just added handling of $String shorter then $Format by adding a side to start the fill and a string length to the while loop.



function str_format_number($String, $Format, $Start = 'left'){

    //If we want to fill from right to left incase string is shorter then format

    if ($Start == 'right') {

        $String = strrev($String);

        $Format = strrev($Format); 

    }

    if($Format == '') return $String;

    if($String == '') return $String;    

    $Result = '';

    $FormatPos = 0;

    $StringPos = 0;

    while ((strlen($Format) - 1) >= $FormatPos && strlen($String) > $StringPos) {

        //If its a number => stores it

        if (is_numeric(substr($Format, $FormatPos, 1))) {

            $Result .= substr($String, $StringPos, 1);

            $StringPos++;

            //If it is not a number => stores the caracter

        } else {

            $Result .= substr($Format, $FormatPos, 1);

        }

        //Next caracter at the mask.

        $FormatPos++;

    }

    if ($Start == 'right') $Result = strrev($Result);

    return $Result;

}


Here's a little addon to the html_substr function posted by fox. 



Now it counts only chars outside of tags, and doesn't cut words.



Note: this will only work in xhtml strict/transitional due to the checking of "/>" tags and the requirement of quotations in every value of a tag. It's also only been tested with the presence of br, img, and a tags, but it should work with the presence of any tag.



<?php

function html_substr($posttext, $minimum_length = 200, $length_offset = 20, $cut_words = FALSE, $dots = TRUE) {

   

    // $minimum_length:

    // The approximate length you want the concatenated text to be   

 



    // $length_offset:

    // The variation in how long the text can be in this example text 

    // length will be between 200 and 200-20=180 characters and the 

    // character where the last tag ends



    // Reset tag counter & quote checker

    $tag_counter = 0;

    $quotes_on = FALSE;

    // Check if the text is too long

    if (strlen($posttext) > $minimum_length) {

        // Reset the tag_counter and pass through (part of) the entire text

        $c = 0;

        for ($i = 0; $i < strlen($posttext); $i++) {

            // Load the current character and the next one

            // if the string has not arrived at the last character

            $current_char = substr($posttext,$i,1);

            if ($i < strlen($posttext) - 1) {

                $next_char = substr($posttext,$i + 1,1);

            }

            else {

                $next_char = "";

            }

            // First check if quotes are on

            if (!$quotes_on) {

                // Check if it's a tag

                // On a "<" add 3 if it's an opening tag (like <a href...)

                // or add only 1 if it's an ending tag (like </a>)

                if ($current_char == '<') {

                    if ($next_char == '/') {

                        $tag_counter += 1;

                    }

                    else {

                        $tag_counter += 3;

                    }

                }

                // Slash signifies an ending (like </a> or ... />)

                // substract 2

                if ($current_char == '/' && $tag_counter <> 0) $tag_counter -= 2;

                // On a ">" substract 1

                if ($current_char == '>') $tag_counter -= 1;

                // If quotes are encountered, start ignoring the tags

                // (for directory slashes)

                if ($current_char == '"') $quotes_on = TRUE;

            }

            else {

                // IF quotes are encountered again, turn it back off

                if ($current_char == '"') $quotes_on = FALSE;

            }

           

            // Count only the chars outside html tags

            if($tag_counter == 2 || $tag_counter == 0){

                $c++;

            }           

                           

            // Check if the counter has reached the minimum length yet,

            // then wait for the tag_counter to become 0, and chop the string there

            if ($c > $minimum_length - $length_offset && $tag_counter == 0 && ($next_char == ' ' || $cut_words == TRUE)) {

                $posttext = substr($posttext,0,$i + 1);               

                if($dots){

                   $posttext .= '...';

                }

                return $posttext;

            }

        }

    }   

    return $posttext;

} 



?>