PHP variable definition, variable, variable reference, and destruction method

Copy codeThe Code is as follows:
<? Php
$ Long = "big_long_variable_name ";
$ Long = "PHP";/* use the string stored in the variable $ long as the name of the new variable, equivalent to $ big_long_variable_name = "PHP ";*/
$ Short = & $ big_long_variable_name;/* assign the value of $ big_long_variable_name to the variable $ short. The value of $ short is "PHP ", equivalent to $ short = & $ long ;*/
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 .*/
Print "02 Long is $ big_long_variable_name.";/* output: 02 Long is PHP .*/
?>
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<? 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. */
Print "03/$ short is $ short";/* output: 03 $ short is PHP rocks! */
Print "04 Long is $ big_long_variable_name";/* output: 04 Long is PHP rocks! */
?>
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05 $ short is PHP rocks!
06 Long is PHP rocks!
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<? 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. */
Print "07/$ short is $ short";/* output: 07 $ short is PHP rocks! Programming PHP rocks! */
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. */
?>
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09 $ short is Programming PHP rocks!
10 Long is Programming PHP rocks!
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<? 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. */
Print "11/$ short is $ short";/* output: 11 PHP rocks! Programming PHP rocks! Web Programming PHP rocks! Programming PHP rocks! */
Print "12 Long is $ big_long_variable_name ";
?>
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<? Php
Unset ($ big_long_variable_name);/* use unset () to destroy the variable $ big_long_variable_name. The variable $ short will not be affected. */
Print "13/$ short is $ short";/* although the variable $ big_long_variable_name is destroyed, $ short is not affected and its value is still the PHP rocks that was last granted! Programming PHP rocks! Web Programming PHP rocks! Programming PHP rocks! */
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 .*/
Snow;
?>
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<? 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 ". */
Print "15/$ short is $ short.";/* output: 15 $ short is No point TEST1 .*/
$ Short = "No point TEST2 $ short";/* value the variable $ short again. No. is added after $ short, but its last value "No point TEST1" is referenced ". */
Print "16/$ short is $ short.";/* output: 16 $ short is No point TEST2 No point TEST1 .*/