Recently, some special PHP symbols were found when I was writing a PHP program, such as less than the symbol consecutively, three smaller than the symbol, eot, eod, echo, and print, suddenly I found that after using PHP for so long, I didn't even fully recognize the basic symbols of PHP. I saw the @ number and found out what it meant for a long time. sort the basic symbols and some common PHP symbols for ice bars on the outside into a list. post them on my blog. If you need them, refer to the special symbols related to PHP ~ Annotation Symbol: // single line annotation/**/The use of multiple line annotation quotation marks ''single quotes, no meaning, without any processing directly;" "Double quotation marks, php dynamically processes and outputs, which are generally used for variables. 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. add the string to the set operation = place the value on the right to the left (always) + = Add the value on the right to the left- = Reduce 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 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 & lt;> (greater than) to & gt; 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 <EOTHTML output content... // Comments are output here! EOT; (Note: "{Variable}" is used for internal variables) 6. Determine whether the file exists and the output content <? Php $ FileName = "File. TXT "; if (File_Exists ($ FileName) {Echo" <xmp> ". file_Get_Contents ($ FileName ). "</xmp>" ;}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 "); the escape line into HTML <BR/> Original: http://y312ff.blog.163.com/blog/static/12701109420119119575812/ lazycms: $ sysname first saw this expression, I would like to ask what is double colon answer: directly belongs to the class of the method or attribute. That is, the use of static methods or attributes. Domain operators are generally used to use the attributes/methods of Class A objects in Class B objects! Class c {private static $ _ memory; public static function autoload () {// method body} c ::$ _ memory; c: autoload ();