PHP variable definition, variable, variable reference, and destruction

<? Php <br/> $ long = "big_long_variable_name"; <br/> $ long = "php "; /* use the string stored in the variable $ long as the name of the new variable, equivalent to $ big_long_variable_name = "php"; */<br/> $ short = & $ big_long_variable_name; /* assign the value of $ big_long_variable_name to the variable $ short. The value of $ short is "php", which is equivalent to $ short = & $ long; */<br/> Print "01/$ short is $ short. ";/*"/$ "is an escape sequence, indicating to output a dollar sign $, the same below. The purpose of this statement is to output: 01 $ short is Php. */<br/> Print "02 long is $ big_long_variable_name. ";/* output: 02 long is Php. */<br/>?> </P> <p> <br/> </P> <p> <? PHP $ big_long_variable_name. = "rocks! ";/* Assign a value to $ big_long_variable_name again. During the value re-assignment process, because the. (point number) is added after $ big_long_variable_name, the value of the variable $ big_long_variable_name should be the original value ("php") + new value ("rocks! "), That is, the current complete value of the variable $ big_long_variable_name is" php rocks! ". The same below. */<Br/> Print "03/$ short is $ short";/* output: 03 $ short is Php rocks! */<Br/> Print "04 Long is $ big_long_variable_name";/* output: 04 Long is Php rocks! */<Br/>?> </P> <p> <br/> </P> <p> 05 $ short is Php rocks! <Br/> 06 long is Php rocks! </P> <p> <br/> </P> <p> <? PHP $ short. = "programming $ short";/* value the variable $ short again. Because. (DOT) is added to the end of $ short, please refer to the above example to analyze the value of $ short. */<Br/> Print "07/$ short is $ short";/* output: 07 $ short is Php rocks! Programming PHP rocks! */<Br/> Print "08 long is $ big_long_variable_name";/* The variable $ short is assigned a new value to programming PHP rocks !, Therefore, the value of $ big_long_variable_name is changed to "php rocks!" together with $ short! Programming PHP rocks! ". Output of this statement: 08 long is Php rocks! Programming PHP rocks! Note: If you destroy unset () for a variable with the same value, the other variable is not applicable to this situation and will not be destroyed together. */<Br/>?> </P> <p> <br/> </P> <p> 09 $ short is programming PHP rocks! <Br/> 10 long is programming PHP rocks! </P> <p> <br/> </P> <p> <? PHP $ big_long_variable_name. = "Web programming $ short";/* The variable $ big_long_variable_name is assigned a new value, and the complete value should be PHP rocks! Programming PHP rocks! WEB programming PHP rocks! Programming PHP rocks !. The value of $ short is consistent with $ big_long_variable_name. For analysis, see comments in section 5th and section 10th. */<Br/> Print "11/$ short is $ short";/* output: 11 PHP rocks! Programming PHP rocks! WEB programming PHP rocks! Programming PHP rocks! */<Br/> Print "12 long is $ big_long_variable_name"; <br/>?> </P> <p> <br/> </P> <p> <? Php <br/> unset ($ big_long_variable_name);/* use unset () to destroy the variable $ big_long_variable_name. The variable $ short will not be affected. */<Br/> Print "13/$ short is $ short";/* although the variable $ big_long_variable_name is destroyed, $ short is not affected, its value is still the last PHP rocks assigned! Programming PHP rocks! WEB programming PHP rocks! Programming PHP rocks! */<Br/> Print "14 long is $ big_long_variable_name.";/* The variable $ big_long_variable_name has been destroyed and therefore has no value. Output: 14 long is. */<br/> snow; <br/>?> </P> <p> <br/> </P> <p> <? PHP $ short = "No point test1";/* value the variable $ short again. Because no. is added after $ short this time, the current value of $ short is "No point test1 ". */<Br/> Print "15/$ short is $ short. ";/* output: 15 $ short is no point test1. */<br/> $ short =" No point Test2 $ short ";/* assign a value to the variable $ short. No. is added after $ short, but its last value "No point test1" is referenced ". */<Br/> Print "16/$ short is $ short.";/* output: 16 $ short is no point Test2 no point test1 .*/