PHP Base _ Variables and comparators

I PHP rookie a, first read "PHP and MySQL Web development", the comparison of some of the basic things listed, convenient and their own rookie quick start, and easy to review their understanding later.

① variable

1. The characteristic should be that the variable does not need to be predefined and can be used directly.

2. The effect of variables placed in single and double quotes is completely different.

1 <? PHP 2         ' myString ' ; 3         ' $test.------ ' ; 4         " $test.------ " ; 5 ?>

The results are shown below

　　

　　Conclusion: Variables can be identified in double quotation marks and can only be used as strings within single quotes

3. String connection with ". ($aaa = $bbb. $CCC)

4. Constants (part of a variable)

A significant difference in the definition of constants and variables is the use of the "$" notation

For example

Define (' AAA ', ' astring ')//constant

$AAA = ' astring ' //variable

② comparison Symbols

1.== (equivalent)

Description

Variables: values are equal.

Array: Contains the same elements.

1<?PHP2$test 1 ='111';3$test 2 =111;4$test 3 = Array (111,222,333);5$test 4 = Array ('222','111','333');6$test 5 = Array ('test1'='111','test2'='222','test3'='333');7$test 6 = Array ('test1'=111,'test2'=222,'test3'=333);8         if($test 1== $test 2) {Echo'Success1';}9         if($test 3== $test 4) {Echo'Success2';}Ten         if($test 5== $test 6) {Echo'SUCCESS3';} One?>

Output Result: SUCCESS1SUCCESS3

2.=== (Identity)

Variables: Both numeric and data types are equal

Arrays: containing the same order and type

<?PHP $test 1='111'; $test 2=111; $test 3= Array (111,222,333); $test 4= Array ('111','222','333'); $test 5= Array ('test1'='111','test2'='222','test3'='333'); $test 6= Array ('test1'=111,'test2'=222,'test3'=333); $test 7= Array ('test3'='333','test2'='222','test1'='111'); $test 8= Array ('test1'='111','test2'='222','test3'='333'); if($test 1=== $test 2) {Echo'Success1';} if($test 3=== $test 4) {Echo'Success2';} if($test 5=== $test 6) {Echo'SUCCESS3';} if($test 5=== $test 7) {Echo'SUCCESS4';} if($test 5=== $test 8) {Echo'SUCCESS5';}?>

Output Result: SUCCESS5

3.0 and not 0

Not 0 is true,0 to False

<? PHP         ' 0 ' ;         1 ;         if ' Success1 ' ;}         if ' Success2 ' ;}? >

Output: Success2 ( in the use = = to make sure to remember not to write less equal sign, written $test1 = ' 0 ')

③ structure

1. Branches (no spaces between ElseIf)

Ifelse  {}

　　　　

　　

PHP Base _ Variables and comparators