PHP Basic Syntax

1. Tags and annotations

<?php

Code

?>

Use the/* */Comment

2. Output statements

echo "Hello", "World"; echo can output multiple strings, separated by commas

print "Hello"; Print can only output one string

3. Data type

PHP is a weakly typed language

Data types can be converted automatically

4. Variable definition

PHP definition variables start with $

$a = 5;

$b = "Hello";

Variable variable:

* $a = "Hello";
$hello = "World";
echo $ $a; Output World

Determine if the variable is defined:

$a = 3;

echo isset ($a); True returns 1, FALSE returns 0

To clear a variable:

unset ($a);

Determine if the variable is empty:

Empty ($a)

Take address:

$a = 5;
$b =& $a; & Take addresses, A and B take the same address in memory, change one, and the other changes
$b = 10;
echo $a; Output 10
Unset ($b); Simply cancels the value association, the referenced variable does not disappear
echo $a; Output 10
Echo $b;

5. Type conversion

$a = 5;
Var_dump ($a); Output variable Details
$b = (string) $a; Type conversions
Var_dump ($b);

6. Operator expressions

Math operators: +-*/% + +--+ = =

$a = 10;
$b = 3;
echo $a/$b; Output 3.33333333333

String: stitching string with dot not with +

echo "Hello". " World ";

Comparison operator: < > <= >== = = =!

Logical operators: and && or | | !

Error control Operator: @

echo @ $a; Can mask errors

Ternary operator:? :

echo true? " Male ": ' Female ';

PHP Basic Syntax