INTRODUCTION

true == 'x'
'x' == 0
0 == false
Thankfully, true != false
but coercions in PHP are weird.




NUMBER --> BOOLEAN

false === (bool) 0
true === (bool) 1
true === (bool) 8

false === (bool) 0.0
true === (bool) 0.1
true === (bool) 0.8




BOOLEAN --> NUMBER

0 === (int) false
1 === (int) true

0.0 === (double) false
1.0 === (double) true




STRING --> BOOLEAN

false === (bool) ''
false === (bool) '0'

true === (bool) '0.0'
true === (bool) '00'
true === (bool) ' 0'
true === (bool) 'a'




BOOLEAN --> STRING (sigh)

'1' === (string) true
'' === (string) false




ARRAY --> BOOLEAN

false === (bool) []
true === (bool) [0]




NUMBER --> STRING

'0' === (string) 0
'0' === (string) 0.0
'1.2' === (string) 1.2
'-1.2' === (string) -1.2




STRING --> NUMBER

123 === (int) '123'
123 === (int) '  123abc456'
0 === (int) ''
0 === (int) 'php'

-2.8 === (double) '-2.8'
1000.0 === (double) '1e3'
1000 === (int) (double) '1e3'
1 === (int) '1e3'




It's probably best just to
avoid == and use === ...

1000 == 1000.0
1000.0 == '1e3'
1000 == '1e3'
1 != '1e3'

1 !== 1.0
1 == 1.0
'1' == '1.0'




., +, -

1 . 2 === '12'
'abc3' + 4 === 4
'56' - '7' === 49

1 + '2abc' . 4 === '34'
78 . 9 - '6' === 783