Summary of PHP common functions (recommended)

1. Write files

1. Open the resource (file) fopen($filename,$mode)
2. Write the file fwrite($handle,$str)
3. Close the file fclose($handle)
4. Write file_put_contents($filename,$str,$mode) in one step FILE_APPEND LOCK_EX
}

2. Read the file
1. Read the file fread($handle, number of bytes)
2. Read a line of fgets( $handle);
3. Read a character fgetc($handle)
4. Read it into an array file($filename)
5. Read file_get_contents($filename) in one step

3. Directory operation
#1, create directory mkdir($dirname)
2, delete the directory rmdir($dirname)
3, open the directory handle opendir($dirname)
4, read the number of directory entries readdir($handle)
5, close the directory resource closedir($handle)
6, reset the directory resource rewinddir($dirname);

4. Directory and file operations
1. Check whether the file or directory exists file_exists($filename)
2. Rename files or directories rename($file)

5. File operations
1Copy file copy('original file','target file')
2Delete file unlink($filename)
3Get file size filesize( $filename)
4 Get the creation time of the file filectime($filename)
5 Get the access time of the file fileatime($filename)
6 Get the modification time of the file filemtime($filename)

6. Path operation1 Get the path dirname($path)
2 Get the file name basename($path)
3 Get the path information pathinfo($path)

7. Array Function (extremely important)

1. Insert an element at the beginning of the array array_unshift($arr,$v)
2. Add an array element at the end of the array array_push($arr,$v ,$v1...)
3. Move the first element out of the array and return this element array_shift($arr)
4. Delete the element array_pop($arr)
5 at the end of the array .Concatenate the array into a string using $separator implode($a,$arr)
6. Check whether the variable is an array is_array($arr)
7. Get the key name of the array array_keys($arr)
8. Get the value of the array array_values($arr)
9. Retrieve whether $value is in $arr, return the Boolean value in_array($v,$arr)
10. Retrieve the array $arr, whether There is the key name $key array_key_exists($k,$arr)
11. Retrieve whether $value is in $arr. If it exists, return the key name Array_search($value, $arr)
12. Reverse an array Sort, if the second parameter is true, keep the key name Array_reverse($arr, true)
13. Exchange the key and value of the array Array_flip($arr)
14. Count the number of array elements Count( $arr)
15. Count the occurrences of all values ​​in the array Array_count_values($arr)
16. Remove duplicate values ​​in the array Array_unique($arr)
17. Sort the values ​​from small to large Sort ($arr)
18. Sort the values ​​from large to small Rsort($arr)
19. Sort the keys from small to large ksort($arr)
20. Sort the keys from large to small krsort($ arr)
21. Randomly obtain $num elements from the array Array_rand($arr, $num)
22. Sum all elements of the array Array_sum($arr)
23. Merge array array_merge( $arr,$arr)

##8. String functions (extremely important)

1. Output the string echo($str) echo
2. Output as it is (distinguish between single quotes and double quotes) print($str)
3. Output the string and end the script execution Die($str ):die($str) die;
4. Output the string and end the script execution exit($str) exit;
5. Output the formatted string printf($str,$p1,...)
6. Do not directly output the formatted string, return the formatted string, and save it to the variable sprintf($str,$p1,...)
7. Print the relevant information of the variable var_dump($ p)
8. Convert the string to lowercase strtolower($str)
9. Convert the string to uppercase strtoupper($str)
10. Convert the first character of the string to uppercase ucfirst( $str)
11. Convert each word in the string to uppercase ucwords($str)
12. Remove the blank characters at both ends of the string. Trim($str,' ,')
13. Remove the blank characters on the left side of the string. Ltrim($str)
14. Remove the blank characters on the right side of the string. Rtrim($str)
Blank characters: "", "\t", "\n", "\r", "\0"
15 Get the string length strlen($str)
16 Count the number of strings included substr_count($str,'substring')
17 Return the substring starting from $start and length $length in the string $string
Substr($string,$start [,$length])
18 Returns the substring from the first occurrence of $search to the end of the string in the string $string.
Strstr($string,$search)
19 Find the first position of $search in $str, starting from $offset.
Strpos($str,$search[,int $offset])
20. Find the last position of $search in $str, starting from $offset
Strrpos($str,$search[, int $offset])
21. Replace all $search in $str with $replace.
Str_replace($search,$replace,$str)
22. Repeat the specified string output
Str_repeat()
23. Encrypt the string
Md5()
24. String flip
Strrev()
25. Use one string to split another string to form an array //Convert the string into an array
Explode("separator",$str);

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