PHP - 「1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf」== 1是真

Question

爲什麼執行以下PHP代碼塊？

if ("1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 1) { 
    echo "WTF!"; 
} 

這大概意味着"1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 1是真的？

對於那些聲明一個字符串總是計算爲真的人，爲什麼下面的代碼塊不能執行？

if ("111987266c1d" == 1) { 
    echo "WTF, again!"; 
} 

Answer 1

當PHP字符串比較爲int，將字符串轉換爲int，這在字符串的開頭只需要數字，結束其中字母開始。我跑通過我鼓搗了幾個測試例子：

[1] > "1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 1; 
// true 
[2] > "1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == '1'; 
// false 
[3] > "1ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 2; 
// false 
[4] > "2ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 2; 
// true 
[5] > "2ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 3; 
// false 
[6] > "2ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 1; 
// false 
[7] > "10ebc0b7ef6141d11989f78748555751721187266c1dd4ece76fec267e5cb1aaf" == 1; 
// false 
[9] > "111987266c1d" == 1; 
// false 

這進一步由documentation備份：

如果你比較了一些用細繩或比較涉及數字字符串，然後每串被轉換爲一個數字，並進行數值比較。