Several program applications of PHP substr() function_PHP tutorial

Introduction to substr() function

The substr() function returns a part of a string.

Syntax: substr(string,start,length).

• string: required. Specifies a part of the string to be returned.
• start: required. Specifies where in the string to begin. Positive number - starts at the specified position in the string; negative number - starts at the specified position from the end of the string; 0 - starts at the first character in the string.
• charlist: optional. Specifies the length of the string to be returned. The default is until the end of the string. Positive number - returned from the position of the start parameter; negative number - returned from the end of the string.

Note: If start is a negative number and length is less than or equal to start, length is 0.

Program List: negative start parameter

<?php
	$rest = substr("abcdef", -1);    // returns "f"
	echo $rest.'<br />';
	$rest = substr("abcdef", -2);    // returns "ef"
	echo $rest.'<br />';
	$rest = substr("abcdef", -3, 1); // returns "d"
	echo $rest.'<br />';
?>

Program execution result:

f
ef
d

Program List: negative length parameter

starts from the start position. If length is a negative value, it starts counting from the end of the string. If substr("abcdef", 2, -1), it starts from c, and then -1 means to intercept to e, which means to intercept cde.

    
<?php
	$rest = substr("abcdef", 0, -1);  // returns "abcde"
	echo $rest.'<br />';
	$rest = substr("abcdef", 2, -1);  // returns "cde"
	echo $rest.'<br />';
	$rest = substr("abcdef", 4, -4);  // returns ""
	echo $rest.'<br />';
	$rest = substr("abcdef", -3, -1); // returns "de"
	echo $rest.'<br />';
?>

Program execution result:

abcde
cde
de

Program List: Basic substr() function usage

<?php
echo substr('abcdef', 1);     // bcdef
echo '<br />';
echo substr('abcdef', 1, 3);  // bcd
echo '<br />';
echo substr('abcdef', 0, 4);  // abcd
echo '<br />';
echo substr('abcdef', 0, 8);  // abcdef
echo '<br />';
echo substr('abcdef', -1, 1); // f
echo '<br />';
// Accessing single characters in a string
// can also be achieved using "square brackets"
$string = 'abcdef';
echo $string[0];                 // a
echo '<br />';
echo $string[3];                 // d
echo '<br />';
echo $string[strlen($string)-1]; // f
echo '<br />';
?>

Program execution result:

bcdef
bcd
abcd
abcdef
f
a
d
f

Program List: Remove suffix

    
<?php
//removes string from the end of other
function removeFromEnd($string, $stringToRemove) 
{
    // 获得需要移除的字符串的长度
	$stringToRemoveLen = strlen($stringToRemove);
	// 获得原始字符串的长度
    $stringLen = strlen($string);
    
	// 计算出需要保留字符串的长度
    $pos = $stringLen - $stringToRemoveLen;
	
    $out = substr($string, 0, $pos);
    return $out;
}
$string = 'bkjia.jpg.jpg';
$result = removeFromEnd($string, '.jpg');
echo $result;
?>

Program execution result:

bkjia.jpg

Program List: If the string is too long, only the beginning and end will be displayed, and ellipses will be used instead

<?php 
$file = "Hellothisfilehasmorethan30charactersandthisfayl.exe"; 
function funclongwords($file) 
{ 
	if (strlen($file) > 30) 
	{ 
		$vartypesf = strrchr($file,"."); 
		// 获取字符创总长度
		$vartypesf_len = strlen($vartypesf); 
		// 截取左边15个字符
		$word_l_w = substr($file,0,15); 
		// 截取右边15个字符
		$word_r_w = substr($file,-15); 
		$word_r_a = substr($word_r_w,0,-$vartypesf_len); 
		return $word_l_w."...".$word_r_a.$vartypesf; 
	} 
	else 
		return $file; 
} 
// RETURN: Hellothisfileha...andthisfayl.exe 
$result = funclongwords($file);
echo $result;
?>

Program execution result:

Hellothisfileha...andthisfayl.exe

Program List: Display extra text as ellipsis

Many times we need to display a fixed number of words, and the extra words are replaced with ellipses.

    
<?php 
$text = 'welcome to bkjia, I hope you can find something you wanted.';
$result = textLimit($text, 30);
echo $result;
function textLimit($string, $length, $replacer = '...') 
{ 
  	if(strlen($string) > $length) 
  	return (preg_match('/^(.*)\W.*$/', substr($string, 0, $length+1), $matches) ? $matches[1] : substr($string, 0, $length)) . $replacer; 
  
  	return $string; 
} 
?>

Program execution result:

welcome to bkjia, I hope...

Program List: Format string

Sometimes we need to format strings, such as phone numbers.

  
<?php
function str_format_number($String, $Format)
{
    if ($Format == '') return $String;
    if ($String == '') return $String;
    $Result = '';
    $FormatPos = 0;
    $StringPos = 0;
    while ((strlen($Format) - 1) >= $FormatPos)
	{
        //If its a number => stores it
        if (is_numeric(substr($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++;
    }
    return $Result;
}
// For phone numbers at Buenos Aires, Argentina
// Example 1:
    $String = "8607562337788";
    $Format = "+00 0000 0000000";
    echo str_format_number($String, $Format); 
	echo '<br />';
// Example 2:
    $String = "8607562337788";
    $Format = "+00 0000 00.0000000";
    echo str_format_number($String, $Format); 
	echo '<br />';
// Example 3:
    $String = "8607562337788";
    $Format = "+00 0000 00.000 a";
    echo str_format_number($String, $Format); 
	echo '<br />';
?>

Program execution result:

+86 0756 2337788
+86 0756 23.37788
+86 0756 23.377 a

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