How to detect if a string contains uppercase letters in php

Two methods: 1. Use strlen() and ord() to check whether each letter is uppercase, the syntax "for($i=0;$i =ord('A')&&ord($str[$i])

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

php checks whether the string contains Capital letters can also be understood as determining whether all letters in a string are lowercase. You can use the following two methods to judge.

Method 1: strlen() ord() function checks whether each letter in the string is uppercase one by one

• Use first Use the strlen() function to get the length of the string and then loop out the individual letters

• Then use the php ord() function to check whether each letter is uppercase

  ord () function can return the ASCII value of a character.

  The ASCII value ranges from 65 to 90, which are 26 uppercase English letters, and the ASCII values from 97 to 122, which represent 26 lowercase English letters.

Just get the ASCII value of the character and check whether it is between 65 and 90.

PHP custom function:

/** * # 检测字符串中是否含有大写字母 * @param string 要判断的字符串 * * @return bool 含有大写字母返回 TRUE 否则返回 FALSE */ function is_bigstr($str) { for ($i = 0; $i < strlen($str); $i++) { if (ord($str[$i]) >= ord('A') && ord($str[$i]) <= ord('Z')) { return true; } } return false; }

Function call:

var_dump(is_bigstr('hello')); // false var_dump(is_bigstr('Hello')); // true

Method 2: Use the preg_match() function to match the regular pattern Expression to detect whether it contains uppercase letters

The preg_match function is used to perform a regular expression pattern match and will return the number of matches of the pattern (0 or 1). 0 means no match, 1 means there is a match.

The regular expression used is:/[A-Z]/, used to find uppercase letters

'; }else{ echo '没有大写字母！
'; } } is_bigstr('hello'); is_bigstr('Hello'); ?>

• There are no uppercase letters in the first string, so there is no match and 0 is returned; and 0 will be automatically converted to FALSE in () of the if statement; therefore, the code in else is executed.
  

• There are uppercase letters in the second string, so there is a match and 1 is returned; and 1 will be automatically converted to TRUE in () of the if statement; therefore, directly Code after executing if.

Recommended learning: "PHP Video Tutorial"

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