How to determine whether it is an integer string in php

Two judgment methods: 1. Use is_numeric() and strpos() to judge whether the string is a numeric string that does not contain a decimal point. The syntax is "!is_numeric($str)||strpos($str," .")!==false", if false is returned, it is an integer string, and vice versa. 2. Use intval() to convert the string into an integer value, and use the "==" operator to determine whether the integer value is equal to the original string. The syntax is "intval($str)==$str".

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

php determines whether a string For an integer string

Method 1: Use the is_numeric() function and strpos() function to judge

You only need to judge whether the string is A numeric string without a decimal point is enough

Example: Check whether the strings "a678", "3.14", and "67854" are integer strings.

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
    if(!is_numeric($str)||strpos($str,".")!==false){
      echo "$str 字符串不是整数字符串<br><br>";
    }else{
      echo "$str 字符串是整数字符串<br><br>";
    }
}
f("a678");
f("3.14");
f("67854");
?>

Analysis:

• is_numeric() function can determine whether it is a number or a numeric string, but it cannot check out the character Whether the string is an integer, that is, the string may be an integer or a floating point number;

• In this case, you need to use strpos() to judge, and use this function to check whether the numeric string contains a decimal point , which excludes floating point numbers.

Description:

intval() function

intval() function To get the integer value of a variable.

intval() function returns the integer value of variable var by using the specified base conversion (default is decimal). intval() cannot be used with object, otherwise an E_NOTICE error will be generated and 1 will be returned.

int intval ( mixed $var [, int $base = 10 ] )

Parameter description:

• $var: The quantity value to be converted to integer.

• #$base: The base used for conversion.

If base is 0, the base used is determined by detecting the format of var:

• If the string includes "0x" ( or "0X"), use hexadecimal (hex); otherwise,

• If the string starts with "0", use octal (octal); otherwise,

• Decimal will be used.

Return value

• Returns the integer value of var on success, and returns 0 on failure. An empty array returns 0, a non-empty array returns 1.

• The maximum value depends on the operating system. The maximum signed integer range on 32-bit systems is -2147483648 to 2147483647. For example, on such a system, intval('1000000000000') would return 2147483647. On a 64-bit system, the maximum signed integer value is 9223372036854775807.

• String may return 0, although it depends on the leftmost character of the string.

Method 2: Use the intval() function and the "==" operator to make a judgment

You only need to convert the string is an integer, and then determine whether the integer is equal to the previous string.

Example:

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
    $result = intval($str);
    if($result==$str){
        echo "$str 字符串是整数字符串<br><br>";
    }
    else{
        echo "$str 字符串不是整数字符串<br><br>" ;
    }
}
f("678");
f("678d");
f("a678");
f("3.14");
?>

Analysis:

• Use the intval() function to convert a string into an integer value
  

• Use the "==" operator to determine whether the integer value is equal to the original string

Instructions :

is_numeric() function

is_numeric() function is used to detect whether a variable is a number or a numeric string.

bool is_numeric ( mixed $var )

• $var: Variable to be detected.

Return value

• If the specified variable is a number or numeric string, it returns TRUE, otherwise it returns FALSE. Note that floating point type returns 1 , that is, TRUE.

strpos() function

strpos() function finds the first occurrence of a string in another string (size sensitive Write).

strpos($string,$find,$start)

• $string : Required. Specifies the string to be searched for.

• #$find: required. Specifies the characters to search for.

• $start: Optional. Specifies the location from which to start the search.

Return value:

• Returns the position of the first occurrence of a string in another string, or returns if the string is not found FALSE. Note: The string position starts from 0, not from 1.

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