


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

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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