PHPの文字列を整数に変換する方法

$num = '345432123';
 
 //（一）
$num = (int)$num;
//输出：
//int(345432123)
 
//（二）
$num = intval($num);
//输出：
//int(345432123)

function convertInt($strInt = ''){ 
    $len = strlen($strInt);  
    $int = 0;
 
    for($i=0;$i<$len;$i++){
        $int *= 10;            
        $num = $strInt{$i} - &#39;0&#39;;            
        $int += $num;        
    }
 
    return $int;        
}
 
 $num = &#39;345432123&#39;;    
 var_dump(convertInt($num)); //输出： int(345432123)
在 Redis 里面也有提供一个字符串转整型的函数，也是通过ascii码方式去做的，实现的比较完善严谨，具体可以参考下
string2ll 函数
#include <stdio.h>
#include <limits.h>
#include <string.h>
 
/* Convert a string into a long long. Returns 1 if the string could be parsed
 * into a (non-overflowing) long long, 0 otherwise. The value will be set to
 * the parsed value when appropriate. */
int string2ll(const char *s, size_t slen, long long *value) {
    const char *p = s;
    size_t plen = 0;
    int negative = 0;
    unsigned long long v;
 
    if (plen == slen)
        return 0;
 
    /* Special case: first and only digit is 0. */
    if (slen == 1 && p[0] == &#39;0&#39;) {
        if (value != NULL) *value = 0;
        return 1;
    }
 
    if (p[0] == &#39;-&#39;) {
        negative = 1;
        p++; plen++;
 
        /* Abort on only a negative sign. */
        if (plen == slen)
            return 0;
    }
 
    /* First digit should be 1-9, otherwise the string should just be 0. */
    if (p[0] >= &#39;1&#39; && p[0] <= &#39;9&#39;) {
        v = p[0]-&#39;0&#39;;
        p++; plen++;
    } else if (p[0] == &#39;0&#39; && slen == 1) {
        *value = 0;
        return 1;
    } else {
        return 0;
    }
 
    while (plen < slen && p[0] >= &#39;0&#39; && p[0] <= &#39;9&#39;) {
        if (v > (ULLONG_MAX / 10)) /* Overflow. */
            return 0;
        v *= 10;
 
        if (v > (ULLONG_MAX - (p[0]-&#39;0&#39;))) /* Overflow. */
            return 0;
        v += p[0]-&#39;0&#39;;
 
        p++; plen++;
    }
 
    /* Return if not all bytes were used. */
    if (plen < slen)
        return 0;
 
    if (negative) {
        if (v > ((unsigned long long)(-(LLONG_MIN+1))+1)) /* Overflow. */
            return 0;
        if (value != NULL) *value = -v;
    } else {
        if (v > LLONG_MAX) /* Overflow. */
            return 0;
        if (value != NULL) *value = v;
    }
    return 1;
}
 
//-------- 执行 ---------
int main(){
    long long num;
    string2ll("345432123",strlen("345432123"),&num);
    printf("%d\n",num); //输出 345432123
    retunr 0;
}