Maison > Article > développement back-end > PHP substr()函数的几个程序应用_PHP教程
substr() 函数返回字符串的一部分。
语法:substr(string,start,length)。
注释:如果 start 是负数且 length 小于等于 start,则 length 为 0。
<?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 />'; ?>
程序运行结果:
f ef d
就是从start位置开始,若length为负值的话,就从字符串的末尾开始数。substr("abcdef", 2, -1)的话,就是从c开始,然后-1说明截取到e,就是要截取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 />'; ?>
程序运行结果:
abcde cde de
<?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 />'; ?>
程序运行结果:
bcdef bcd abcd abcdef f a d f
<?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; ?>
程序运行结果:
bkjia.jpg
<?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; ?>
程序运行结果:
Hellothisfileha...andthisfayl.exe
很多时候我们需要显示固定的字数,多出的字数用省略号代替。
<?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 $string; } ?>
程序运行结果:
welcome to bkjia, I hope...
有时候我们需要格式化字符串,比如电话号码。
<?php function str_format_number($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 />'; ?>
程序运行结果:
+86 0756 2337788 +86 0756 23.37788 +86 0756 23.377 a