Common PHP symbols and functions

Variable form: True or False; False is False. common variable form: string (numbers, Chinese characters, etc) integer (1, 2, 3, 4, 5, 0,-1,-2, and so on) double floating point number (decimal point) array object method available... "> <LINKhref =" http: // www. php1

 

Variable form: True or False; False is False. common variable form: string (numbers, Chinese characters, etc) integer (1, 2, 3, 4, 5, 0,-1,-2, etc.) double floating point number (decimal point) the methods available for array object objects include gettype ($ mix) and settype ($ mix, $ typename ); common symbols \ "double quotes \ backslash \ n line feed \ r output \ t hop (TAB) operator Number + addition operation-subtraction operation * multiplication operation/division operation % remainder operation + + accumulation-subtraction 1. set the string addition operation = place the value on the right to the left (Yes) + = add the value on the right to the left-= decrease the value on the right to the left * = multiply the value on the left by the value on the right/= and divide the value on the left by the value on the right. = add the string on the right to the left operator operation & and | or ^ mutex (xor) <shift to left> Shift to the right ~ The complement logical operation of 1 is <less than> greater than <= less than or equal to> = greater than or equal! = Not equal to & and | or! No other operator number $ variable symbol & variable indicator (before the variable) @ do not display error information (before the function)-> object method or attribute => array element value? : Basic method of ternary computation. 1. PHP converts strings to uppercase and lowercase! Strtolower (); convert character to lower case strtoupper (); convert character to upper case 2. PHP encrypted string (case sensitive) md5 (); encrypted sha1 (); encrypted 3. quotation marks 1, single quotation marks are output as is 2, double quotation marks are content interpretation for output 3, and single quotation marks are executed as a command, such as 'pwd '. 4. "\" acts on translated characters. for example, "\ n" is a line break! 4. function: htmlspecialchars () this function converts special characters into HTML strings (&....; ). The most common use case may be the message board for handling customer messages. & (And) to & "(double quotation marks) to" <(less than) to <> (greater than) to> This function only converts the preceding special characters, not all are converted to the ASCII conversion defined in HTML. 5. batch output HTML content! Echo <EOTHTML output content... // Comments are output here! EOT; Print <". File_Get_Contents ($ FileName )."";}Else {Echo" no ";}?> 7. unset; unset ($ var); unset ($ var, $ var1); 8. is_int; check whether the variable is an integer; 9. is_null; check whether the variable is NULL; 10. is_string checks whether the variable is a string 11. is_real; alias of is_float () 12. isset check whether the variable is set 13. is_bool checks whether the variable is Boolean 14. is_array checks whether the variable is an array. is_object checks whether the variable is an object 16. subStr. SUBSTR (String, Start, SelectNum) echo substr ('abcdef', 1); // bcdefecho substr ('abcdef', 1, 3 ); // bcdecho substr ('abcdef', 0, 4); // abcdecho substr ('abcdef', 0, 8); // abcdefecho substr ('abcdef',-1, 1); // f17.Nb2brecho nl2br ("foo isn't \ n bar"); convert the escape line to HTML