Learn how to remove other characters from PHP strings, leaving only numbers

In the previous article "PHP String Learning: Dividing Strings into Substrings of Smaller Length", we introduced the method of splitting strings and dividing strings into smaller substrings. This time I will continue to learn and practice PHP strings and see how to extract numeric characters in strings. If necessary, you can refer to it~

The theme of this article is: "Extracting numeric characters from strings". For example, if we give the following string

$str ='0我是123456一段测试的字789符串0';

, how can we remove other characters and only return the substring "01234567890" composed of the numeric characters in the string? Here are two methods to introduce to you:

First look at the first method:

<?php
header("content-type:text/html;charset=utf-8");
function findNum($str) {
	$str = trim($str);
	if (empty($str)) {
		echo &#39;&#39;;
	}else{
		$temp = array(&#39;1&#39;, &#39;2&#39;, &#39;3&#39;, &#39;4&#39;, &#39;5&#39;, &#39;6&#39;, &#39;7&#39;, &#39;8&#39;, &#39;9&#39;, &#39;0&#39;);
		$result = &#39;&#39;;
		for ($i = 0; $i < strlen($str); $i++) {
			if (in_array($str[$i], $temp)) {
				$result .= $str[$i];
			}
		}
		echo $result;
	}
}
$str = &#39;0我是123456一段测试的字789符串0&#39;;
findNum($str);
?>

Analyze the above code:

• Use trim($str) to remove the spaces at both ends, and use the if statement to ensure that the string after removing the spaces is not an empty string.
  

• Create a character array containing numbers 0~9 respectively$temp
  

• Use The for loop traverses the string $str, compares each character in $str with the elements in the $temp array, and obtains the numeric characters. (Use the in_array function to search whether each character in $str exists in the $temp array, so you can determine whether the character is a numeric character).

• Use ".=" to splice the obtained numeric characters together, and then output the spliced ​​string.

Look at the output:

OK, it is the numerical substring "01234567890" that needs to be returned at the beginning of the article!

The following introduces The second method is similar to the first method, except that the in_array() function is replaced by the is_numeric() function.

<?php
header("content-type:text/html;charset=utf-8");
function findNum($str) {
	$str = trim($str);
	if (empty($str)) {
		echo &#39;&#39;;
	}else{
		$result = &#39;&#39;;
		for ($i = 0; $i < strlen($str); $i++) {
			if (is_numeric($str[$i])) {
				$result .= $str[$i];
			}
		}
		echo $result;
	}
}
$str = &#39;0我是123456一段测试的字789符串0&#39;;
findNum($str);
?>

Analyze the above code:

• Use a for loop to traverse the string $str, but this time without using the numeric character array and in_array () function to determine whether it is a numeric character, use the is_numeric() function directly. The is_numeric() function can detect whether a variable is a number or a numeric string.

• Use is_numeric($str[$i]) in the loop body to determine whether the $str[$i] character is a number character; if so, take it out and use ".=" to concatenate it into a numeric substring.

Look at the output:

Okay, that’s all. If you want to know anything else, you can click this . → →php video tutorial

Finally, I recommend reading a classic course "PHP String Processing (Jade Girl Heart Sutra Edition)", it's free~ come and learn !

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