How to check if a value is a string in php

Detection method: 1. Use the is_string() function to detect whether the variable is a string type. If it returns true, it is a string, and vice versa. 2. Use the var_dump() function to output relevant information about the variable, including the type and value of the expression; if the output result contains "string", it means it is a string.

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

Method 1: Use is_string( ) Function

is_string() detects whether the variable is of string type, and the return value is true or false. It can be understood here that it only detects the type. Even if a variable is empty, it will return true as long as it is a string type.

bool is_string ( mixed $var )

• $var: Variable to be detected.

Return value

• If the specified variable is a string, TRUE is returned, otherwise FALSE is returned.

Example

<?php
header("Content-type:text/html;charset=utf-8");
$str="2663";
echo "值 ".$str."，";
if ($str)
    echo &#39;是一个字符串。&#39; . PHP_EOL;
else
    echo &#39;不是一个字符串。&#39;;

?>

##Method 2: Using the var_dump() function

var_dump() function is used to output relevant information about variables.

var_dump ($expsn)

• $expsn: Specify the variable you want to output. It can be a single variable or an expression containing multiple space-separated variables of any type.

Return value: No return value.

The var_dump() function displays structural information about one or more expressions, including the type and value of the expression. Arrays will expand values ​​recursively, showing their structure through indentation.

Tip As well as outputting the results directly to the browser, you can use the output control function to capture the output of the current function and then (for example) save it to a string.

Example:

<?php
var_dump(2663);
var_dump("2663");
?>

• If the output result contains "string", it means is a string.

Extended knowledge: print_r() and var_dump() are similar

The print_r() function is used to print variables in a more understandable form, The content and structure of the entire array can be output through the print_r() function, and the keys and elements will be displayed in a certain format.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr=array("姓名"=>"张三","年龄"=>25,"性别"=>"男");
print_r($arr);
?>

Output result:

The difference between print_r() and var_dump():

Use the print_r() function to print out the entire Array content and structure, display keys and elements according to a certain format. Note that the print_r() function is not just for printing, it is actually used to print easy-to-understand information about the variables.

var_dump() function can also be used to print the data and structure of the array. However, the var_dump() function is more powerful than print_r(). It can print multiple variables at the same time and give the type information of the variables.

var_dump() function displays structural information about one or more expressions, including the expression's type and value. Arrays will expand values ​​recursively, showing their structure through indentation.

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