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strlen
strlen() can return the "length" of a "string " .
grammar
int strlen( $str )
parameter
- $str : the string whose length needs to be calculated
return value
Returns the length "number of bytes" of the string , and returns 0 for an empty string, NULL, or false.
1. String
Passing "string" as a parameter will return the length of the string, which is also the most commonly used method.
Example:
var_dump(strlen('1234'));
var_dump(strlen('abcd'));
output:
int(4)
int(4)
Two, spaces
strlen() calculates the number of "bytes" rather than the number of "characters" . When a "space" is encountered , the length will also be +1.
Example:
# 一个空格
var_dump(strlen(' '));
# 两个空格
var_dump(strlen(' '));
# 字符中夹杂空格
var_dump(strlen('a b c '));
output:
int(1)
int(2)
int(6)
3. Integers and decimals
Although strlen() requires parameters of string type to be passed in, the length can also be calculated by passing in a "numeric type" . Integers and decimals are the same as strings, and the number of bytes will be calculated.
Example:
var_dump(strlen(123));
var_dump(strlen('123'));
var_dump(strlen(123.1));
var_dump(strlen('123.1'));
output:
int(3)
int(3)
int(5)
int(5)
4. Boolean type
The "Boolean type" is special, true returns 1, false returns 0.
Example:
var_dump(strlen(true));
var_dump(strlen(false));
output:
int(1)
int(0)
Five, translation characters
"Translation character" counts as one byte, length +1, but it needs to be wrapped in "double quotes" , and single quotes will be treated as a string.
Example:
var_dump(strlen("\n"));
var_dump(strlen("\n\r"));
var_dump(strlen('\n'));
output:
int(1)
int(2)
int(2)
6. Arithmetic operators
When the parameter passed in is "without quotation marks" and contains "arithmetic operators" , strlen() will perform the operation first, and then calculate the length of the operation result.
Example:
var_dump(strlen(1+1));
var_dump(strlen(5*5));
var_dump(strlen('1+1'));
output:
int(1)
int(2)
int(3)
Example: Reverse ~ will also be calculated first, and then calculate the length of the operation result
var_dump(strlen(~~10));
var_dump(strlen(~10));
output:
int(2)
int(3)
Seven, logical operators
When the parameter passed in is "without quotation marks" and contains "logical operators" , strlen() will perform the operation first, and then calculate the length of the operation result.
Since the results of logical operators are true or false , their return results are both 1 or 0.
Example:
var_dump(strlen(1&1));
var_dump(strlen(1|0));
var_dump(strlen(!1));
output:
int(1)
int(1)
int(0)
8. Special symbols
The "special symbol" of "English" is counted as one byte, and the length is +1; the "special symbol " of "Chinese" is counted as three bytes, and the length is +3.
Example:
var_dump(strlen("；"));
var_dump(strlen(";"));
var_dump(strlen('，'));
var_dump(strlen(','));
output:
int(3)
int(1)
int(3)
int(1)
9. Chinese
The Chinese characters of "UTF8 encoding" occupy 3 bytes, and the length is +3; the Chinese characters of purple "GB2321 encoding" occupy 2 bytes, and the length is +2.
Example:
var_dump(strlen("中文"));
var_dump(strlen('中文'));
output:
int(6)
int(6)
10. Empty and NULL
When $str is "empty string" or NULL , return length 0.
Example:
var_dump(strlen(''));
var_dump(strlen(null));
output:
int(0)
int(0)